(Bloomberg) -- Donald Trump will campaign in three western states over the next week, going to the mat in a bid to maintain or possibly increase the Republican majority in the U.S. Senate in the Nov. 6 midterm elections.

Trump’s western swing will take him to Missoula, Montana, on Oct. 18; Mesa, Arizona, on Oct. 19; and Elko, Nevada, on Oct. 20, White House officials said.

The week’s events will be in support of Republican Senate candidates, including state auditor Matt Rosendale, who’s challenging Democratic incumbent Senator Jon Tester in Montana. Recent polls suggest Tester has a narrow lead in a state Trump won easily in 2016.

In Arizona, which also backed Trump in 2016, Republican Martha McSally is going against Democrat Krysten Sinema for the Senate seat being vacated by Republican Jeff Flake. The race is essentially a toss-up. In Nevada, a state Trump lost in 2016 to Democrat Hillary Clinton, Republican incumbent Dean Heller is in a close race with Democrat Jacky Rosen.

Trump, 72, has campaigned for at least 17 House candidates since late August, including five House races this week alone. He’s spending Saturday night in Richmond, Kentucky, campaigning on behalf of Andy Barr, a Republican incumbent in the House who is locked in a tight race with Democrat Amy McGrath, a retired U.S. Marine.

Trump has been doing so many rallies, with such largely repetitive rhetoric, that cable networks -- even Fox News -- have stopped airing them in full. 

His visit to Iowa earlier this week coincided with the start of early voting in both Iowa and Nebraska. Campaign aides said their rosters show that between 30 percent and 45 percent of audiences at Trump rallies are Democrats and independents.

To contact the reporter on this story: Jennifer Jacobs in Washington at jjacobs68@bloomberg.net

To contact the editors responsible for this story: Ros Krasny at rkrasny1@bloomberg.net, John McCluskey

©2018 Bloomberg L.P.