Scan: Who will win the next presidential election?

← Back to scans

Who will win the next presidential election? — Marco Rubio

KXPRESPERSON-28-MRUB · Elections · 2026-04-06

Agent

13%

Market Price

-3.6%

Edge

35%

Confidence

Final Rationale

My revised independent estimate of ~4% was driven by the strong base rate that sitting VPs almost always seek the nomination (~85%), making it unlikely Rubio even runs given his public pledge to defer to Vance. The Devil's Advocate correctly identified that my original Vance-running probability (60%) and pledge-breaking probability (20%) were poorly calibrated; correcting these significantly lowered my estimate from 7% to ~4%. The market at 12.6% with very high depth suggests traders are pricing in meaningful probability of scenarios where Vance's political position deteriorates sufficiently over the next 3 years that Rubio's candidacy becomes viable — perhaps through Iran war fallout, midterm losses, or economic downturn hurting the incumbent party's heir apparent. I deviate below the market because the structural constraint of a sitting VP usually running is very strong, but I move substantially from my independent estimate toward the market given the genuine uncertainty over a 3-year horizon.

Price vs. prediction

How the market moved after the agent's call. Solid blue line is the actual market price; dashed line is the agent's static forecast at $t{=}0$.

$n = 52$ follow-ups

1. Planner Opus · Fermi decomposition + tool plan

Tools chosen: kalshi_data kalshi_orderbook article_search web_search wikipedia_lookup code_execution

Sub-questions (Fermi decomposition)

Will Marco Rubio seek the Republican presidential nomination in 2028? (w=0.25)
If Rubio seeks the Republican nomination, will he win it? (w=0.35)
If Rubio wins the Republican nomination, will he win the 2028 general election? (w=0.40)

Planner reasoning

This question requires a three-stage conditional probability analysis: (1) Does Rubio run? — Rubio is currently Secretary of State under Trump, which is both a platform and a potential constraint. Historical Secretaries of State rarely win the presidency in the modern era (Hillary Clinton being the most recent major attempt). Rubio has long harbored presidential ambitions (ran in 2016), and serving as SoS under a popular predecessor creates both name recognition and a succession narrative. (2) Can Rubio win the GOP primary? — The 2028 Republican field will be wide open. Key competitors include JD Vance (sitting VP, historically advantaged), Ron DeSantis, Glenn Youngkin, and others. Rubio must navigate being seen as Trump's loyal subordinate while also distinguishing himself. The VP historically has a strong path. (3) Can Rubio win the general? — In 2028, the incumbent party (Republicans) will face the typical incumbency headwinds after potentially 8 years in power, though 2028 is only the second term of a Trump-era cycle. The critical difference here is that this is NOT a Trump succession question from 2024 — it's whether Rubio specifically beats all comers. The key analytical frame is: P(Rubio wins) = P(Rubio runs) × P(Rubio wins primary | runs) × P(Rubio wins general | wins primary). Current prediction market prices from Kalshi will be the most informative data point, supplemented by polling and political landscape analysis.

2. Research Parallel tool calls · legacy v2

Tool	Status	Time	Items
kalshi_data	OK	2.2s	-
kalshi_orderbook	OK	0.2s	-
article_search	OK	1.1s	-
web_search	OK	50.8s	-
wikipedia_lookup	OK	2.1s	-
code_execution	OK	0.0s	-

3. Evidence Synthesis Sonnet · 19 items · legacy v2

#	Strength	Credibility	Direction	Source	Claim	Priced In
1	MODERATE	-	↓ DOWN	web_search	Rubio has publicly stated he will not run for president in 2028 if JD Vance seeks the GOP nomination, though many GOP insiders believe this commitment is less ironclad than it appears.	Yes
2	MODERATE	-	↑ UP	web_search	A 'Draft Rubio' donor movement is forming, and America 2100 — a political nonprofit run by Rubio's close advisers founded in 2023 — could serve as a campaign infrastructure launchpad if circumstances change.	No
3	MODERATE	-	NEUTRAL	web_search	Trump polled GOP donors at Mar-a-Lago and they overwhelmingly supported Rubio; Trump himself said Vance was 'most likely' the heir to MAGA and 'probably favored at this point,' not Rubio.	No
4	STRONG	-	↑ UP	article_search	Rubio's profile has grown dramatically in early 2026, serving as Secretary of State, acting National Security Advisor, and playing a central role in the Venezuela Maduro capture operation and the Iran war.	Yes
5	MODERATE	-	↑ UP	web_search	Following Rubio's prominent role in the Iran war (March 2026), speculation increased significantly that Rubio would run in 2028 despite his earlier pledge to defer to Vance.	No
6	MODERATE	-	↓ DOWN	code_execution	Historically, 37.5% of Secretaries of State ran for president, but in the modern era (post-WWII), only 1 of 13 ran and none won, suggesting the SoS role is not a reliable presidential launching pad in the modern era.	Yes
7	STRONG	-	↑ UP	wikipedia_lookup	The 2028 election is confirmed to be open — Trump is ineligible for a third term due to the 22nd Amendment, making 2028 the first election since 2012 without Trump as the Republican nominee.	Yes
8	MODERATE	-	NEUTRAL	kalshi_data	Kalshi's overall market for Rubio winning the 2028 presidency sits at 12.60%, which implicitly caps the probability of Rubio running at a moderate-to-low level given the subsequent conditional hurdles.	Yes
9	MODERATE	-	↓ DOWN	web_search	JD Vance, as sitting VP, is widely viewed as the frontrunner for the 2028 GOP nomination, with Trump publicly calling him 'most likely' the MAGA heir and 'probably favored'; Rubio has pledged not to challenge Vance.	Yes
10	MODERATE	-	↓ DOWN	web_search	GOP donors are 'quietly discussing' a Rubio 2028 bid and he faces 'real formidable obstacles' running against the VP, indicating Rubio would not be a clear favorite even if he entered.	No
11	WEAK	-	↑ UP	web_search	Questions are 'quietly emerging over Vance's inevitability' as Rubio's profile and responsibilities have expanded, suggesting the primary race may not be as settled as Vance's VP status implies.	No
12	MODERATE	-	↓ DOWN	kalshi_data	The Trump family member nominee market sits at 15%, indicating meaningful competition for the nomination from non-Vance/non-Rubio sources, further fragmenting any probability Rubio could win the primary.	Yes
13	MODERATE	-	↓ DOWN	code_execution	In the modern era, no Secretary of State who ran for president ultimately won; Hillary Clinton (2016) being the closest modern attempt, and she lost both the general and to a primary challenger in 2008.	Yes
14	MODERATE	-	↓ DOWN	kalshi_data	The Republican party is priced at 40.60% to win the 2028 presidential election, down 4.4% over the past 30 days, suggesting the GOP faces meaningful headwinds in the general election — relevant to Rubio's chances if nominated.	Yes
15	MODERATE	-	NEUTRAL	kalshi_data	The 2028 election is priced at 93% probability of occurring in 2028, providing a baseline context that eliminates most tail risk around election cancellation or postponement.	Yes
16	MODERATE	-	NEUTRAL	article_search	A war with Iran was ongoing as of March 2026, with energy crisis concerns growing; geopolitical instability could cut either way for Republican general election prospects in 2028 depending on outcomes.	No
17	MODERATE	-	NEUTRAL	article_search	Trump was attempting to 'nationalize' the 2026 midterm elections and reshape election administration rules, creating significant uncertainty around electoral fairness and norms in 2028.	Yes
18	WEAK	-	↑ UP	web_search	Rubio's SoS role has given him significant foreign policy credentials (Venezuela, Iran war), which historically can be an asset in general elections against Democratic opponents.	Yes
19	STRONG	-	↓ DOWN	kalshi_orderbook	The Kalshi orderbook for Rubio winning 2028 shows high liquidity (depth 197,925 contracts), yes_bid at $0.03 and no_bid at $0.77, with a wide $0.20 spread indicating significant uncertainty but a market leaning heavily toward NO.	Yes

Information Gaps

No data on JD Vance's own Kalshi market price for 2028, which would be the most useful arbitrage comparison for sq2
No polling data on Republican primary voters' preferences among Vance, Rubio, and other potential candidates
No data on whether Vance has formally announced or strongly signaled a 2028 run, which would be the key trigger for Rubio's decision
No analysis of 2028 Democratic field strength, which affects sq3 general election probability
No information on Rubio's personal fundraising activity or donor outreach for 2028
No data on how the Iran war outcome (ongoing as of March 2026) might affect GOP general election prospects in 2028
No information on midterm 2026 results and their implications for 2028 party dynamics
No current polling on Rubio's general election favorability vs. potential Democratic opponents
No clarity on whether Trump would endorse Vance or Rubio if both were to run

Key Uncertainties

Whether JD Vance will formally announce a 2028 campaign — if he does, Rubio's stated pledge not to run becomes the binding constraint
Whether Trump will formally endorse Vance or potentially shift support toward Rubio, which would be decisive in the GOP primary
The outcome and public perception of the Iran war — success could boost Rubio's profile; failure could damage administration figures
Whether the 'Draft Rubio' donor movement gains enough momentum to make Rubio's pledge to defer to Vance untenable
The 2026 midterm results and whether they strengthen or weaken incumbency advantage for Republicans heading into 2028
How election rule changes being pursued by Trump in 2026 might affect general election dynamics in 2028
Whether Rubio's testimony in the Rivera trial creates any political liability

Market Context

Price: 0.126 · 7d: +0.003 · 30d: +0.006
Volume: HIGH — 17,048 average daily contracts for the Rubio market is substantial · Depth: VERY HIGH — 197,925 contracts depth
Reliability: HIGH — Very high volume and depth; the market is actively traded and the price of 12.6% reflects the full conditional chain (runs × wins primary × wins general); the wide spread ($0.20) and the yes_bid at only $0.03 vs no_bid $0.77 suggests the market is heavily skewed toward NO; Republican party win market at 40.6% provides useful upper bound context

4. Independent Forecaster Opus · No market price · legacy v2 Did NOT see market price

Independent estimate: 7% (45% confidence)

sq1: Will Marco Rubio seek the Republican presidential nomination in 2028?

40%

Base rate: Rubio has long harbored presidential ambitions (ran in 2016), and the 2028 race is open. However, he has publicly stated he won't run if Vance seeks the nomination. Key factors pushing UP: His profile has grown enormously as SoS (Iran war, Venezuela operation), a 'Draft Rubio' donor movement is forming, America 2100 infrastructure exists, and Trump's Mar-a-Lago poll showed donors preferred Rubio. These push up by ~15% from a base of ~25%. Key factors pushing DOWN: His public pledge to defer to Vance is a significant constraint (-10%), and Trump has publicly called Vance 'most likely' the heir (-5%). The critical uncertainty is whether Vance actually runs — if Vance runs (which seems likely given he's VP), Rubio's pledge becomes binding unless circumstances dramatically change. I estimate ~60% chance Vance runs, in which case Rubio probably doesn't (~80% he honors pledge). If Vance doesn't run (~40%), Rubio very likely runs (~85%). So: P(runs) ≈ 0.6 × 0.2 + 0.4 × 0.85 = 0.12 + 0.34 = 0.46. Adjusting slightly down for general uncertainty and the fact that even without Vance, Rubio might choose to stay in his SoS role: ~0.40.

sq2: If Rubio seeks the Republican nomination, will he win it?

35%

Base rate: In a competitive GOP primary with no incumbent, any individual candidate's chance of winning is roughly 15-25% depending on field size. However, if Rubio is running, it likely means either (a) Vance isn't running (in which case Rubio would be a frontrunner, ~40-50% chance) or (b) Rubio broke his pledge because circumstances changed dramatically (in which case it's a tough fight against the sitting VP, ~15-20% chance). Weighting these scenarios: If Rubio runs, I estimate ~70% chance it's because Vance isn't running and ~30% chance he runs despite Vance. So: P(wins primary | runs) ≈ 0.7 × 0.45 + 0.3 × 0.18 = 0.315 + 0.054 = 0.37. Pushing DOWN slightly: No modern SoS has won a primary/general, and the field will include other strong candidates (DeSantis, Youngkin, etc.). Pushing UP slightly: Rubio's expanded profile from Iran war and Venezuela operation. Final estimate: ~0.35.

sq3: If Rubio wins the Republican nomination, will he win the 2028 general election?

47%

Base rate: The party holding the White House for 8 years wins the next election roughly 40% of the time in the post-WWII era (succeeded: 1988 Bush; failed: 1960, 1968, 2000, 2008, 2016). This gives a base of ~33% (1/6 clear successes, though 2000 was extremely close). However, pushing UP: If Rubio is the nominee, he would be a strong general election candidate — Hispanic heritage, Florida senator, foreign policy credentials, moderate-enough appeal. The Iran war outcome is uncertain but could boost him if successful. Also, structural changes to election administration under Trump could advantage Republicans (+5%). Pushing DOWN: 8-year fatigue, potential economic headwinds from tariffs/Iran war energy crisis, and the Democratic opponent is unknown but could be strong. The 2028 Democratic field might include strong governors or fresh faces. Net assessment: The Republican nominee in 2028 has roughly a 45% base chance (adjusting the historical 33% upward due to current Republican structural advantages in the Electoral College and potential election rule changes). Rubio specifically might be slightly better than a generic Republican due to Hispanic appeal and foreign policy credentials (+2%). Final: ~0.47.

Show full reasoning trace

base rate: For any specific named politician to win a presidential election 3 years out, the base rate is quite low — typically 5-15% for frontrunners and 1-5% for second-tier candidates. Rubio is somewhere in between: he's a prominent Cabinet member with presidential ambitions but has publicly deferred to the sitting VP. Historical base rate for Secretaries of State winning: 0% in modern era.

evidence updates: Key upward shifts: Rubio's dramatically expanded profile from Iran war and Venezuela operations (+), Draft Rubio donor movement (+), Trump donor poll favoring Rubio (+). Key downward shifts: Public pledge to defer to Vance (-), Trump calling Vance 'most likely' heir (-), no modern SoS has won (-). The Iran war is the biggest wildcard — its outcome could dramatically shift Rubio's prospects either way.

combination method: Conditional probability chain: P(runs) × P(wins primary | runs) × P(wins general | wins primary). Each conditional is estimated independently, accounting for the selection effects (e.g., if Rubio runs, it likely means Vance isn't running, which changes the primary dynamics).

final: Marco Rubio has approximately a 7% chance of being inaugurated as president in January 2029. The biggest bottleneck is whether he runs at all (40%), followed by winning a competitive primary (35% conditional on running), and then winning the general election (47% conditional on being nominee). The estimate reflects significant uncertainty about whether Vance runs, the Iran war outcome, and the broader political landscape in 2028.

5. Devil's Advocate Sonnet · legacy v2 Market price revealed

Reasoning Flaw Missing Info

Challenges

The conditional probability chain math checks out (0.40 × 0.35 × 0.47 = 0.0658 ≈ 0.07), so the arithmetic is sound. However, the decomposition has a subtle issue: the sq3 estimate of 47% for a Republican winning the general election seems too low relative to the forecaster's own reasoning. The forecaster adjusts the historical base rate of ~33% up to 47% citing structural Republican advantages, but simultaneously notes Republican party win market is at 40.6%. If we take the market's 40.6% as the general election probability, this would lower the final estimate slightly.
The 60% probability assigned to Vance running seems potentially too low given that Vance is the sitting VP with Trump's explicit endorsement as 'most likely' heir. Historically, sitting VPs almost always seek their party's nomination when eligible (Bush 1988, Gore 2000, Biden considered in 2016 before declining, Harris 2024). The base rate for a sitting VP seeking the nomination is probably 80-90%, not 60%. This would significantly reduce P(Rubio runs) and thus the final probability.
The forecaster assigns 20% probability that Rubio breaks his public pledge if Vance runs. This seems quite high for a politician in a Cabinet role who made the pledge publicly and repeatedly. Breaking such a pledge would be politically costly and would alienate Trump's base. A more realistic estimate might be 5-10%, which would further reduce P(Rubio runs).
The forecaster notes 'no modern SoS has won' as a downward factor but may be underweighting this. It's not just a statistical coincidence — the role of SoS is fundamentally different from governor or senator in terms of building a primary campaign infrastructure, maintaining domestic political networks, and connecting with voters on kitchen-table issues. This structural disadvantage should perhaps pull the primary win probability lower.
The information gap about Vance's market price is significant. If Vance is trading at, say, 20-25% on Kalshi (plausible for a sitting VP), then the combined Rubio + Vance probability would need to be consistent with the overall Republican party probability of 40.6%. This provides an important cross-check that the forecaster doesn't perform.
The forecaster's confidence level of 0.45 seems appropriate given the massive uncertainty, but the 1311 days to resolution means enormous amounts of information will emerge. The Iran war outcome, 2026 midterms, economic conditions, and Vance's decision will all be known well before resolution. Given this extreme uncertainty, the forecast should perhaps have wider error bars rather than a precise-seeming 7%.

Suggested adjustment: -2pp

The 60% estimate for Vance running is likely too low — sitting VPs almost always seek the nomination (base rate ~85%). If we adjust to 80% Vance runs, then P(Rubio runs) = 0.80 × 0.10 + 0.20 × 0.85 = 0.08 + 0.17 = 0.25 (using a more conservative 10% pledge-breaking rate). Also adjusting primary win probability slightly: P(wins primary | runs) stays around 0.35. This gives 0.25 × 0.35 × 0.47 = 0.041, or roughly 4-5%. However, there's genuine uncertainty about whether Vance's political position weakens enough that the pledge becomes moot, and the Iran war wildcards could dramatically shift dynamics. A modest downward adjustment to ~5.5% seems warranted based on the Vance base rate correction.

Market comparison: Forecaster: 7%, Market: 12.6%. The forecaster is actually BELOW the market by 5.6 percentage points. The market's higher price could reflect traders pricing in scenarios where Vance doesn't run or where Rubio's foreign policy profile becomes dominant. However, given the reasoning flaws identified (underestimating Vance's likelihood of running, overestimating Rubio's pledge-breaking probability), the forecaster's estimate should arguably be even lower than 7%, not higher. The market at 12.6% may be overpricing Rubio given the Vance constraint, or may have information about Vance's political trajectory that isn't captured here.

6. Aggregator Opus · final calibrated forecast

9% (35% confidence)