Trump's impeachment last week by the House of Representatives for his role in inciting the riot at the U.S. Capitol set up his trial in the Senate. But there's one potential wrinkle.

In 2019, the last time Trump found himself impeached by the House, he had nearly a year left in his presidency. But on Wednesday, with the inauguration of Joe Biden, Trump will be out of office by the time any Senate trial gets started.

Some Republican lawmakers argue it's not constitutional to hold an impeachment trial for a former president, but that view is far from unanimous. Democrats for their part appear ready to move forward with a trial.

On Tuesday, Sen. Joni Ernst, R-Iowa, said she doesn't think a post-presidency impeachment trial is constitutional. But Sen. John Cornyn, R-Texas, wasn't so sure.

"I think there's serious questions about it," he said.

Connecticut Democrat Richard Blumenthal, meanwhile, said it was "bogus" that a trial after Trump leaves office wouldn't be constitutional, noting that the Senate has held impeachment trials of federal judges after they've resigned.

"So whether somebody resigns, or runs out the clock it makes no difference. They can still be held accountable and there's nothing in the spirit, or the letter of the impeachment provisions in the Constitution that argues against it," he said.

Some questions and answers about whether a former president can be impeached.

The Constitution says: "The President ... shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors."

But the Constitution says nothing about the impeachment of a former president. The question has also never come up. The only other two presidents to be impeached, Bill Clinton and Andrew Johnson, were tried while still in office.

A recent Congressional Research Service report for federal lawmakers and their staffs concluded that while the Constitution's text is "open to debate," it appears most scholars agree that a president can be impeached after leaving office. One argument is that state constitutions that predate the U.S. Constitution allowed impeachment after officials left office. The Constitution's drafters also did not specifically bar the practice.

Still, the text of the Constitution could be read to suggest impeachment only applies to current office holders. In the early 19th century, one influential Supreme Court justice, Joseph Story came to that conclusion.

One powerful suggestion that post-office trial is acceptable, however, comes from history. The Congressional Research Service report cites the 1876 impeachment of Secretary of War William Belknap. Belknap resigned over allegations he received kickbacks. The House impeached him after his resignation, and while Belknap objected to being tried in the Senate because he'd left office, the Senate heard three days of arguments on the topic and then deliberated in secret for over two weeks before concluding Belknap could be tried. He was ultimately acquitted.

Courts are unlikely to want to wade into any dispute over impeachment. In 1993, in a case involving an impeached former judge, the Supreme Court ruled it had no role to play in impeachment disputes because the Constitution says the "Senate shall have sole Power to try any impeachments."

One other issue is who would preside at the impeachment trial of an ex-president. The Constitution says it's the chief justice's job to preside at the impeachment trial of a president. But scholars offer differing views about whether that's Chief Justice John Roberts' job if Trump's trial begins after he's out of office.

The choices for who would preside appear to be Roberts, Kamala Harris, who by then will be vice president, or Sen. Patrick Leahy, D-Vt., who will be the Senate's president pro tempore once the Democrats take control of the Senate.

The consequence the Constitution sets up for a president who is impeached and convicted is removal from office. That's not really a concern for a former president. Still, conviction would send a message about Trump's conduct. Moreover, if the Senate were to convict, lawmakers would presumably take a separate vote on whether to disqualify Trump from holding future office. Some lawmakers believe that's appropriate.

"We need to set a precedent that the severest offense ever committed by a president will be met by the severest remedy provided by the Constitution - impeachment and conviction by this chamber, as well as disbarment from future office," incoming Senate majority leader Chuck Schumer, D-NY, said Tuesday.