The Senate trial of former President Donald Trump for one article of impeachment — incitement of the insurrection at the Capitol on Jan. 6 — starts Tuesday with a debate over whether the Constitution allows for prosecution of a president once he leaves office. The debate comes about a year after the Senate acquitted then-President Trump on two counts of abuse of power and obstruction.

Senators will convene in the same chamber that they had to evacuate after a mob breached the building and threatened then-Vice President Mike Pence and top congressional leaders. That siege, just one month ago, left five dead, including a U.S. Capitol Police officer.

The building is still surrounded by a 7-foot-tall security fence, and National Guard troops have joined the Capitol Police to provide a more muscular defense in and around the Capitol complex. Due to the coronavirus pandemic, senators may spread out in the chamber to sit in the public galleries that have been closed to tours for months.

First, a debate about the Constitution

Senate Majority Leader Chuck Schumer and Senate Minority Leader Mitch McConnell negotiated a resolution that guides how the trial will work and structured the trial to kick off with an issue that constitutional scholars don't completely agree on. Tuesday will feature a debate lasting up to four hours, equally divided between the two sides, on this central question underpinning the trial: Is Trump subject to the jurisdiction of the Senate court of impeachment for acts committed during his time as president, even though his term has expired?

After that debate, the Senate will vote on the question and whether a majority agrees the trial will proceed.

Schumer attempted to provide a prebuttal to the claims from the defense team, saying that the argument that the trial is unconstitutional is a "fringe legal theory that has been roundly debunked by constitutional scholars from across the political spectrum." He cited an editorial from Chuck Cooper, a conservative attorney who has represented House Republicans, that ran in Monday's Wall Street Journal.

Impeachment managers maintained in their pretrial brief that Trump was "singularly responsible" for whipping up a crowd of his supporters at a rally outside the White House the morning of Jan. 6, the day Congress was required to count and certify the electoral votes. They also argue that a president must "answer comprehensively for his conduct in office from his first day in office through his past" and that there is "no January exception" to impeachment from any provision in the Constitution. They also point to precedent of another Senate trial — of William Belknap in 1876. He resigned as war secretary but still faced articles of impeachment from the House for corruption and a Senate trial.

Trump's lawyers — Bruce Castor Jr., David Schoen and Michael van der Veen — spent much of their 78-page filing on Monday previewing what they are expected to say when it's their turn to present. They insist the Senate does not have jurisdiction to hold a trial because Trump is no longer serving in office so he cannot be removed.

Kentucky Republican Sen. Rand Paul raised a point of order about the constitutionality of moving forward with the trial last month when senators were sworn in as jurors. Only five GOP senators — Sens. Susan Collins of Maine, Lisa Murkowski of Alaska, Ben Sasse of Nebraska, Mitt Romney of Utah and Pat Toomey of Pennsylvania — voted with Democrats to say the trial should proceed. Many viewed that as a test vote for how many Republican votes there could be to convict the former president. If all Democrats vote to convict, they would need 17 GOP senators to join them to reach the two-thirds threshold. If that happens, the Senate would then vote on whether to bar Trump from running for any future federal office.

Trial comes as GOP debates its future post-Trump

In the immediate aftermath of the January riot, many congressional Republicans criticized Trump and specifically called him out for his role fomenting the attack on the Capitol. It appeared many were ready to move on after spending the last fours years largely in lockstep with the president's positions and dodging questions about his controversial tweets.

McConnell said "the mob was fed lies." He added that "they were provoked by the president and other powerful people, and they tried to use fear and violence to stop a specific proceeding of the first branch of the federal government, which they did not like."

The top House Republican, Rep. Kevin McCarthy, opposed impeachment but argued that Trump "bears responsibility" for the attack.

But in the weeks since the attack, the grip that Trump holds on his party appeared to still be tight. The 10 House Republicans who backed impeachment have faced threats and, in many cases, censure from their local and state party leaders. Several House GOP members pushed for Wyoming Rep. Liz Cheney, the No. 3 House GOP leader who voted for the impeachment resolution, to step down from her post. After a lengthy and contentious meeting about her position, she won a vote to remain as the House GOP conference chair, with a sizable majority backing her in a secret ballot. But Cheney faces a primary challenge for her 2022 reelection.

Senators from both parties acknowledge that the votes aren't there to convict Trump. Virginia Democratic Sen. Tim Kaine floated the idea of censuring the former president, and he has talked to Republicans about the proposal. But Schumer insists the trial is needed so that every senator must go on the record to say whether Trump is guilty of inciting the mob that was intent on interfering in counting the electoral votes and ensuring a peaceful transfer of power.

While Kaine and some other Democrats worry about the trial interfering with confirming President Biden's nominees and work on his chief domestic priority of getting his $1.9 trillion COVID-19 relief package through the Congress, Schumer insists the chamber can multitask.

House Speaker Nancy Pelosi, D-Calif., noted that the impeachment managers will present their case to the senators, who sit as jurors in the trial, but also noted they will also make their case "in the court of public opinion."

"We'll see if it's going to be a Senate of courage or cowardice," Pelosi said last week.

Regardless of the outcome of the Senate trial, the events of Jan. 6 exposed fissures in the GOP that will have an impact on the 2022 midterms. Four Senate Republican incumbents up for reelection have announced they plan to retire at the end of their terms.

McCarthy traveled to Mar-a-Lago, in Florida, last month to meet with Trump to secure the former president's commitment that he would be involved in helping GOP candidates in the midterms, a sign that Trump continues to be the leader of the party and — so far — just a small contingent in the House and Senate appear willing to break with him.

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