Liberals are arguing President Trump could be subject to an impeachment trial even after President-elect Joseph R. Biden is sworn into office, urging lawmakers to move forward with a second impeachment of the sitting president just days before the incoming administration takes control.

A spokesperson for the progressive Constitutional Accountability Center is circulating a law review article and opinions from legal and political pundits championing for the legality of an impeachment trial even after a president leaves office in order to hold him or her accountable, writing “the Senate need not complete a trial before he leaves office” in an email to reporters.

Though the Constitution outlines a president can be impeached for high crimes and misdemeanors, it does not provide a specific time frame.

“It would make no sense for former officials, or ones who step down just in time, to escape that remedial mechanism,” wrote Michael J. Gerhardt, a law professor at the University of North Carolina, in a blog post. “It should accordingly go without saying that if an impeachment begins when an individual is in office, the process may surely continue after they resign or otherwise depart.”

Mr. Gerhardt’s opinion was included in the email circulated by the Constitutional Accountability Center, along with a Texas law review article written by Brian C. Kalt, arguing for the constitutionality of late impeachment.

Democrats have been pushing for Mr. Trump to be impeached a second time, arguing that he incited his supporters to break into the Capitol in a violent riot that ended with several deaths. They argue the president should never be able to serve in office again and that an impeachment would be a path to ensuring so.

If a president is impeached in the House and convicted by the Senate, the upper chamber then holds a second vote to bar the individual from serving in higher office again. It would require 67 senators to accomplish their goal.

House Speaker Nancy Pelosi, in a letter to her colleagues, said she has asked Vice President Mike Pence to invoke the 25th Amendment to remove Mr. Trump, who she said is unstable to continue to serve.

She warned if Mr. Pence does not take action, they could move forward in Congress to hold Mr. Trump responsible for the actions of his supporters following a speech he delivered from the White House on Wednesday just prior to the violence breaking out on Capitol Hill.

“If the President does not leave office imminently and willingly, the Congress will proceed with our action,” Ms. Pelosi wrote.

Mr. Trump has been telling his voters the 2020 election was stolen due to alleged fraud. Election officials from several swing states have dismissed the claims.

Ms. Pelosi’s chamber impeached Mr. Trump over a call with the Ukrainian president in late 2018, and the Senate held a trial early last year. The Republican-controlled chamber did not vote to remove him at that time.