The comments came after three days of opening arguments from House impeachment managers and as the president's legal team started to lay out its case in a brief Saturday session.

"I'm as impartial as I can possibly be, as I've always been. I'm wide open on this, and we'll see where the facts go," Manchin said.

Sen. Doug Jones. (D-Ala.) said he believes House Democrats have made a "compelling case" but added that he wants to listen to the defense being mounted by Trump's legal team.

"I'm hoping to hear the facts and the rebuttal from the president. So I think that's only appropriate," Jones said.

Manchin and Jones, who hail from deeply red states, are viewed by Republicans as two of the Democrats most likely to vote to acquit Trump.

GOP senators previously told The Hill that they believe the vote to acquit Trump will be bipartisan. Sen. Kyrsten Sinema (D-Ariz.) has been tight-lipped about her thinking but is also viewed as a potential swing vote.

"It wouldn't surprise me if we got one or two Democrats. It looks to me over in the House, the Republicans seem to be solid and the Democrats seem to be divided," McConnell said last year.