Former President Donald Trump finally took the plunge into the Ohio Republican primary to potentially succeed retiring Sen. Rob Portman, throwing his weight behind Hillbilly Elegy author and venture capitalist J.D. Vance.

Trump’s endorsement could be a significant test of his continuing influence over the Republican primary electorate. Vance has run on a full-throated platform of populism and national conservatism, suggesting that Americans dying from fentanyl should get more attention than the Russian invasion of Ukraine. Unlike Mehmet Oz, the Trump-endorsed candidate for Senate in Pennsylvania, Vance is a favorite of the MAGA smart set, typified by billionaire and GOP megadonor Peter Thiel.