WASHINGTON (AP) — There's a border crisis in Pennsylvania. The radical left is surging in New Jersey. And Nancy Pelosi is a threat to New York.

Republican candidates in the nation's premiere midterm battlegrounds have embraced a central message in their fight to maintain the House majority this fall — and it has little to do with the surging economy or the sweeping tax cuts that the GOP celebrated as a once-in-a-generation achievement just eight months ago.

Instead, as Republicans enter the final month of the primary season, they're looking ahead to a general-election strategy of embracing anx...