Senator Katie Britt of Alabama was the latest national Republican to visit Iowa to campaign for Representative Ashley Hinson. President Trump will follow on Thursday.
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.