Sixty-seven senators would need to vote to convict Trump. That means a united Democratic caucus plus 17 GOP senators.
Some Republicans say they're still waiting to hear both sides.
"You don't make a decision as a juror until you hear both sides, period, end of story," said Sen. Bill Cassidy of Louisiana. "And so that's why if you ask me the questions I wish to have addresses, I would like to have those addressed, but I don't make a decision until I have heard the other side."
Conviction requires a supermajority of 67 votes.