The worries cut both ways for Democrats and Republicans in the Senate.

Senators in both parties predict impeachment will further polarize the electorate, a troubling development for Republicans running in states won by Democrat Hillary Clinton in the 2016 presidential race such as Sens. Cory Gardner (R-Colo.) and Susan Collins (R-Maine).

Yet for GOP candidates running in states where Trump has a higher approval rating, such as Sens. Thom Tillis (N.C.), Joni Ernst (Iowa) and Mitch McConnell (Ky.), the polarized electorate could help drive Republicans to the polls.

And impeachment proceedings could spell doom for Sen. Doug Jones, a Democrat up for reelection in Alabama, one of the nation's most pro-Trump states. 

Jones told The Hill on Wednesday that he's not thinking about the impact on his reelection.