6% — Will Marco Rubio defeat Gavin Newsom in the 2028 presidential election, with Gavin Newsom as the Democratic nominee and Marco Rubio as the Republican nominee Kalshi 6% · 6 contracts · $34 volume · medium confidence Updated 2026-07-14 09:23:58 UTC Why this matters: This probability represents the chance that Marco Rubio defeats Gavin Newsom if both become their parties' 2028 presidential nominees. The 7% figure reflects market assessments that while Newsom securing the Democratic nomination is moderately plausible (24¢ implied probability), Rubio winning the general election against him is considered unlikely. The current level is driven by two main considerations: Newsom's relative strength in general-election matchups versus other potential Republican candidates, and historical patterns where incumbent-party nominees face headwinds after serving for extended periods. The biggest near-term catalyst will be the 2026 midterm results in November, which typically signal broader electoral trends and could shift perceptions of each candidate's viability. Additionally, any major economic data, foreign policy developments, or shifts in either candidate's political standing before the 2028 conventions would significantly alter these probabilities. Key factors: - Newsom's 24¢ nomination probability implies markets see him as a credible but not heavily favored Democratic candidate, requiring Rubio to clear higher odds in a general matchup - Rubio's 23¢ Republican nomination probability suggests meaningful uncertainty about whether he secures the GOP nomination, directly capping the joint scenario's probability - Historical data shows general-election matchup polls 2+ years before the election have limited predictive power, but current head-to-head metrics between these candidates would inform traders - 2026 midterm performance will provide signals about national sentiment and either candidate's coattails, potentially shifting both nomination and general-election probabilities - Economic conditions and incumbent approval ratings between now and November 2028 are major variables that typically determine general-election outcomes Contracts: - Will Marco Rubio defeat Gavin Newsom in the 2028 presidential election, with Gavin Newsom as the Democratic nominee and Marco Rubio as the Republican nominee?: Marco Rubio defeats Gavin Newsom — 11¢ Kalshi $34 (weight 100%) - Will Gavin Newsom defeat JD Vance in the 2028 presidential election, with Gavin Newsom as the Democratic nominee and JD Vance as the Republican nominee?: Gavin Newsom defeats JD Vance — 6¢ Kalshi $0 (weight 0%) - Will JD Vance defeat Gavin Newsom in the 2028 presidential election, with Gavin Newsom as the Democratic nominee and JD Vance as the Republican nominee?: JD Vance defeats Gavin Newsom — 8¢ Kalshi $0 (weight 0%) - Will Alexandria Ocasio-Cortez defeat JD Vance in the 2028 presidential election, with Alexandria Ocasio-Cortez as the Democratic nominee and JD Vance as the Republican nominee?: AOC defeats JD Vance — 4¢ Kalshi $0 (weight 0%) - Will Alexandria Ocasio-Cortez defeat Marco Rubio in the 2028 presidential election, with Alexandria Ocasio-Cortez as the Democratic nominee and Marco Rubio as the Republican nominee?: AOC defeats Marco Rubio — 3¢ Kalshi $0 (weight 0%) - Will Jon Ossoff defeat Marco Rubio in the 2028 presidential election, with Jon Ossoff as the Democratic nominee and Marco Rubio as the Republican nominee?: Jon Ossoff defeats Marco Rubio — 4¢ Kalshi $0 (weight 0%) --- ## Methodology SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours. ## SF Signal - SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration. - No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only. --- *Last verified: 2026-07-14T09:20:49.801Z* By SimpleFunctions — https://simplefunctions.dev/ Cite as: "6% per prediction markets (SimpleFunctions, July 2026)" Canonical: https://simplefunctions.dev/answer/presoutcome Full data: https://simplefunctions.dev/api/public/query?q=Will%20Marco%20Rubio%20defeat%20Gavin%20Newsom%20in%20the%202028%20presidential%20election%2C%20with%20Gavin%20Newsom%20as%20the%20Democratic%20nominee%20and%20Marco%20Rubio%20as%20the%20Republican%20nominee Provider: SimpleFunctions — https://simplefunctions.dev