Trader consensus on Polymarket positions HHS Secretary Robert F. Kennedy Jr. as the frontrunner at 49% implied probability for the 2028 Republican presidential nomination, reflecting his high-profile role in the Trump administration and the growing Make America Healthy Again movement appealing to voters focused on health policy and vaccine skepticism. Vice President J.D. Vance follows at 36.5%, buoyed by his position as presumptive heir apparent, while Secretary of State Marco Rubio holds 20.2% amid reports of donor preference over Vance in informal White House soundings earlier this month. With President Trump term-limited, the open primary has seen RFK Jr.'s odds surge since mid-March on effective cabinet performance and crossover appeal, though traditional polls favor figures like Donald Trump Jr.; upcoming 2026 midterms and potential endorsements could shift dynamics in this closely contested early field.