Three Republican primaries in May will determine whether President Trump's grip over the GOP is strong or any cracks are forming. Trump has endorsed challengers to Republican incumbents in Indiana, Louisiana, and Kentucky, in each case ignoring lawmakers who resisted his demands. The White House is involved in these efforts, including shaping the favored candidates' strategies and helping them raise money. The upcoming primaries could determine the president's power over Congress and Republican voters, potentially cementing his transition from the GOP to the MAGA party. Meanwhile, the president is focusing on state legislative races in Indiana to oust five Republican lawmakers who blocked his effort to redraw its congressional map.