Former New Jersey governor and ABC News Contributor Chris Christie told ABC News Chief Anchor George Stephanopoulos that Trump’s incitement of the Capitol siege is an impeachable offense.

“If inciting to insurrection isn’t, then I don’t really know what is,” he said Sunday on ABC's "This Week."

House Speaker Nancy Pelosi, in a new letter to Democrats on Saturday, asked members to prepare to return to Washington this week -- another signal that the House could take up and pass the impeachment article to the Senate after it is formally introduced on Monday.

Pelosi thanked fellow Democratic representatives for speaking with her on a conference call Friday and said she was taking their considerations into account. She did not specifically mention voting on impeachment in the letter, though.

"Since that call, I have received scores of communications from Members expressing your views about how we go forward and regarding a strong presence of our Caucus in the Capitol," she wrote. "Over the last few days, I have discussed your views with Constitutional lawyers, both inside and outside the Congress, to consider the parliamentary and constitutional options available to us."

"From what I have heard from Members, and from the deluge that I have received from the public, it is clear that, once again, the Times Have Found Us to save our democracy," Pelosi added in the letter. "We will be proceeding with meetings with Members and Constitutional experts and others. I continue to welcome your comments. I urge you to be prepared to return to Washington this week."

While Democrats are hopeful Republicans will back their effort, none have come out and said they would back the charge as drafted.

Pelosi said at a press conference on Thursday, "If the Vice President and Cabinet do not act [on the 25th Amendment], the Congress may be prepared to move forward with impeachment."

Some Democrats planned to connect with Republican colleagues this weekend to gauge their support and encourage them to back the effort.

-ABC News' Benjamin Siegel

President Donald Trump is leaning toward a legal team led by his current personal lawyer, Rudy Giuliani, as well as longtime ally Alan Dershowitz if he were to face an impeachment trial in the Senate, sources told ABC News.

Dershowitz was one of a number of lawyers who assisted Trump in his first impeachment trial last January. While he was impeached in the House, he was not convicted by the Senate]().

Lawyers Jay Sekulow and Pat Cipollone are not expected to be involved this time around after working on the president's legal team last year, sources said.

House Democrats discussed impeaching the president in the wake of the siege on the U.S. Capitol, egged on by Trump during a rally hours earlier, on Friday. They circulated the draft of a single article citing "incitement of insurrection" that could be introduced as early as Monday. A full House vote could be held as early as the middle of next week.

Trump would have just nine days left in office on Monday and it's legally murky whether an ex-president can be impeached after leaving the presidency.

-ABC News' Katherine Faulders and John Santucci

Vice President Pence will attend President-elect Joe Biden's inauguration, according to a person familiar with his decision.

This comes the day after President Donald Trump tweeted he would not be attending.

On Friday morning, as Pence departed the White House, his press secretary, Devin O’Malley, said, "Vice President Pence and the second lady have yet to make a decision regarding their attendance."

Biden said Friday he would welcome Pence’s attendance, though he hadn't spoken to him about it.

"He's welcome. I think it's important that as much as we can stick to what have been the historical precedence of how and the circumstances of which an administration changes, should be maintained," Biden said. "And so ... the vice president is welcome to come, we would be honored to have him there, and to move forward in the transition."

-ABC News' Katherine Faulders

At District of Columbia Mayor Muriel Bowser's request, Army Secretary Ryan McCarthy has activated about 340 unarmed D.C. National Guardsmen to assist local law enforcement with the demonstrations taking place on Wednesday pegged to the Electoral College certification.

"We think it's helpful to have our D.C. Guardsmen, who are our Guard, that I have requested from the Secretary of the Army to assist MPD [Metropolitan Police Department] with traffic management," Bowser said Monday. "It absolutely frees up more officers."

The D.C. Guard is unique in that any call-ups have to be made by the Army secretary and not the jurisdiction’s top elected official -- as is the case with state governors. Additionally, more focus has been given to the call-ups since the controversial presence of D.C. Guardsmen and the use of D.C. Guard helicopters during the Black Lives Matter demonstrations last summer.

"They will be deployed to assist us with crowd management, as well as traffic control in our nation's capital that will allow for the police officers to focus on anyone who's intent on instigating agitating or participating in violence in our city," said D.C. Police Chief Robert Contee. He also labeled any possibility of violence surrounding the protests as "unacceptable" and repeated that carrying firearms is not allowed under D.C. law.

A senior defense official said Bowser put in the request for Guardsmen on Dec. 31 and that it was approved Monday morning. Beginning Tuesday through Thursday, the 340 personnel will help man 30 traffic control checkpoints around the northern side of the downtown area close to the National Mall.

"No one's going to be armed or body armor or anything like that," said the official. "What they need is traffic control."

-ABC News' Luis Martinez and Quinn Owen