Republican candidates in marquee Senate races have welcomed Thune's help as he's traveled around the country in the weeks before the midterm elections, scrambling to save his majority.
Democrats are targeting G.O.P. strongholds that could set them up for new majorities. But if they don’t win those races now, it could be a long time before they have another chance.
Protesters outside of an event for Senator Roger Marshall in Topeka, Kan. Soaring fuel costs and economic struggles have made some Republican senators like Mr. Marshall vulnerable on their home turf.