Trump is the first U.S. president to be impeached twice and the first to face trial after leaving office. If convicted, the Senate could then vote to bar him from running for office again.

Conviction is seen as unlikely, however, as at least 17 Republicans in the 100-seat chamber would have to join all 50 Democrats to find the former president guilty.

Only six Republicans voted with Democrats to move forward with the trial, rejecting an argument made by other Republican Senators that the Constitution does not allow Congress to impeach a president who has already left office.

The Senate is due to convene at 10 a.m. (1500 GMT), and a final vote could come in the afternoon.

The trial has highlighted the extraordinary danger lawmakers faced on Jan. 6, when Trump urged his followers to march to the Capitol and “get wild” in an effort to prevent lawmakers from certifying his defeat to Democrat Joe Biden in the presidential election. Five people died in the chaos.

Security-camera footage shown at the trial showed rioters came perilously close to lawmakers as they were evacuated from the Senate and the House of Representatives.

Among those targeted was Vice President Mike Pence, who had refused Trump’s entreaties to interfere with the proceedings earlier that day.

Trump criticized Pence on Twitter as lacking “courage” shortly after Republican Senator Tommy Tuberville told Trump that the vice president was being evacuated for his own safety.

Trump’s lawyers gave conflicting answers on Friday when asked if Trump knew Pence was in danger when he issued his tweet. Several Republican senators said they still had questions about Trump’s role.

“The issue is what was the president’s intent, right? Only the president could answer. And the president chose not to,” Republican Senator Bill Cassidy told reporters. He said he had not made up his mind on how to vote.