Rubio leads the Republican VP nominee 2028 market at 31.5% largely due to his role as Secretary of State, which supplies national visibility, foreign-policy credentials, and establishment networks in a wide-open field where the presidential nominee remains undetermined. Vance's sitting vice presidency and other administration figures trail because traders price in potential ticket-balancing needs, Senate experience, and coalition appeal. Key differentiators include governing records, primary performance, and donor alignment, with consolidation likely hinging on 2026 midterm results, early polling trends, and signals from party leadership that could elevate one contender over fragmented alternatives below 10%.