The party apparatus is taking advantage of its enormous war chest, as well as a Supreme Court campaign-finance ruling this year, to send tens of millions into congressional races.
Vice President JD Vance, appearing at a rally in Harlingen, Texas, for some of the Republican candidates in the state, has led the party’s finance operation.
Farmers and ranchers have supported President Trump for a decade. But the war in Iran, tariffs and other administration policies have soured some on the G.O.P.