The campaign arm of Senate Republicans is beginning to roll out a barrage of ads in battleground states as part of a $100 million investment to retake a majority in the chamber in November.

On Thursday, the National Republican Senatorial Committee began to place multimillion-dollar reservations for TV and digital advertising in the fall for four states: Ohio, Nevada, Michigan, and Arizona. Ohio and Nevada are rated toss-ups by the nonpartisan election forecaster Cook Political Report, while the other two are viewed as competitive.