Now, several moderate Republicans, including Sens. Mitt Romney and Susan Collins, have indicated that they will support Democrats’ efforts to call witnesses, which will likely result in increased delays with a possible vote on Friday.

While the exact timetable for the trial remains unclear, here’s what you can expect to happen in the coming days:

Impeachment trial schedule

Tuesday

1 p.m.: Senate trial begins.

The president’s legal team is expected to finish its defense. After that, senators will have 16 hours — likely over two days — to ask questions of their own.

Wednesday-Thursday

1 p.m.: Senate trial begins.

Friday

1 p.m.: Senate trial begins.

Senators are expected to vote on whether to call additional witnesses.

Saturday

It remains unclear whether there will be a Saturday session.

Where to livestream this week's opening arguments

You can watch livestreams for major impeachment events on Politico.com. Keep up with the latest developments from our journalists on Twitter.

Where senators stand on impeachment

Keep track of which Senators are for and against removing Trump from office, and where they stand on the House impeachment efforts.