Several incumbent Democratic senators are trying to win re-election in states that typically vote for Republicans, among them Claire McCaskill of Missouri and Jon Tester of Montana, who are both locked in close contests with Republican challengers. New CBS News Battleground Tracker polling find Tester is up two points with likely voters over Republican Matt Rosendale, 47-45 percent in Montana, while in Missouri, McCaskill and Republican John Hawley are even in support among likely voters at 45-45 percent. Most supporters of all these candidates describe themselves as enthusiastic about voting this year.

In Montana, the candidates predictably split the voters who see a Senate vote as a chance to support or oppose President Trump, but Tester gains from getting more of the voters who say the president is not a factor. Jon Tester is helped by a majority 53 percent approval on handling his job as senator, and he enjoys a ten-point gap among registered voters on which candidate understands the needs and problems of Montana “a lot.”