Acting Homeland Security Secretary Chad Wolf is resigning from the Trump administration effective at 11:59 p.m. Monday, according to an internal message sent to staff at the department, citing "recent events."

"I am saddened to take this step, as it was my intention to serve the Department until the end of this Administration. Unfortunately, this action is warranted by recent events, including the ongoing and meritless court rulings regarding the validity of my authority as Acting Secretary. These events and concerns increasingly serve to divert attention and resources away from the important work of the Department in this critical time of a transition of power," he said in an email to colleagues.

-ABC News' Luke Barr

The House of Representatives is expected to return at 9 a.m. Tuesday to debate and pass a bill via a roll call vote demanding Vice President Mike Pence mobilize the Cabinet to remove Trump from office through the 25th Amendment. The vote is expected around 7:30 p.m., according to House Majority Leader Steny Hoyer’s office.

Democrats will give Pence "24 hours after passage" to respond, said House Speaker Nancy Pelosi in a statement earlier Monday, otherwise they will likely move forward with an impeachment vote on Wednesday, setting up Trump to be the first president in U.S. history impeached twice.

“The President’s threat to America is urgent, and so too will be our action,” Pelosi said in the statement.

As of right now, no Republicans have signed on to the legislation that calls on Pence to invoke the 25th Amendment, which is a likely indicator as to what happens with a potential vote on impeachment.

But sources tell ABC News that it’s possible some Republicans may vote to impeach Trump.

The single article of impeachment charging Trump with “incitement of insurrection” also cites Trump's call with the Georgia Republican secretary of state where he urged him to "find" enough votes for Trump to win the state and, separately, cites the Constitution's 14th Amendment, noting that it "prohibits any person who has 'engaged in insurrection or rebellion against' the United States" from holding office.

-ABC News' Mariam Khan

Acting Homeland Security Secretary Chad Wolf said Monday that in light of the "the evolving security landscape leading up to the inauguration and at the recommendation of Secret Service Director James Murray," he is going have the Secret Service designate the inauguration as a "National Special Security Event" beginning on Wednesday, Jan. 13, as opposed to Jan. 19 as previously slated.

District of Columbia Mayor Muriel Bowser called on the Department of Homeland Security in an earlier press conference for the delegation to begin on Monday.

She also asked the Department of Interior to cancel all public gathering permits in the District through Jan. 24 and urged Americans not to travel to the nation's capital for the inauguration.

Starting this week and running through at least Inauguration Day, armed protests are being planned at all 50 state capitols and at the U.S. Capitol, according to an internal FBI bulletin obtained by ABC News.

-ABC News' Aaron Katersky and Luke Barr

The number of National Guard troops deployed around next week's inauguration could rise from at least 10,000 to 15,000, the National Guard’s top general said Monday.

"Support requests from the Secret Service, Capitol Police and Park Police have been authorized to provide up to 15,000 Guard members to meet current and future support requirements," Gen. Daniel Hokanson, the chief of the National Guard Bureau, told reporters on a phone briefing. "They are troops that have been requested to support security, logistics liaison and communication missions."

Hokanson said that there are currently 6,200 Guardsmen in the District, and there would be 10,000 in place by Saturday.

The National Guard has always participated in inaugurations, and there were 9,000 members on hand last year, but because of the coronavirus pandemic, the number had been reduced to 5,000 for 2021. Last week's insurrection at the Capitol changed those plans, and Pentagon spokesperson Jonathan Hoffman additionally made clear that the Guardsmen will be remaining in Washington after Inauguration Day.

"We're not looking at Jan. 20 as the last day and people will pack up and go home at the conclusion of all the events," he said. "There will be some elements that will remain for a brief period to ensure safety and security in the days following the inauguration as well."

Hokanson, the chief of the National Guard Bureau, said no decision has been made yet about whether to arm the Guardsmen but characterized that possibility as an "ongoing discussion."

"Obviously, we're very concerned that we want our individuals to be have the right to self defense," he said.

-ABC News' Luis Martinez

Rep. Steve Scalise, R-La. -- the No. 2 Republican in the House -- was the last to speak for the Republican Party, said he opposed the "rushed" impeachment, and emphasized that the Senate will only be able to take up the trial once Trump is out of office.

"I've seen the dark evil of political violence firsthand. And it needs to stop. But all of us need to be unequivocal in calling it out every single time we see it, not just when it comes from the other side of the aisle," he said.

Invoking President Abraham Lincoln, he closed by calling on Americans to unify and "seek higher ground."

House Judiciary Chairman Rep. Jerry Nadler, D-N.Y., quickly responded to his remarks, saying, "We can have all this, and we can have accountability too," before handing off to Majority Leader Rep. Steny Hoyer, D-Md.

Hoyer, in a scathing rebuke of the president, repeated the words of Rep. Liz Cheney and called on his Republicans colleagues to rise to the moment and join her to "reject the vices we abhore."

"It is the first and only physical presence other than the 9/11 attack on this nation -- which came from abroad with a plane aimed at our Capitol dome. This attack was not from abroad. It was as Liz Cheney said, summoned, assembled, and inflamed by the president of the United States of America," he said.

"Last Wednesday, on Jan. 6, the nation and the world watched it shatter to pieces. There could be no mistaking any longer the kind of man sitting in the Oval Office or his intentions and capabilities. The curtain has been pulled back. The office to which he was elected could not temper or reform him," Hoyer said.

"Reject deceit. Reject fear mongering. Reject sedition, tyranny and insurrection," Hoyer said. "Reject one man over fidelity to one's country."

Hoyer noted that soon the House Reading Clerk will call the roll for voting, and added, "Make no mistake, this will be no ordinary roll call."

"These votes will be inscribed on the roll of history -- a record of courage -- and of our commitment to country and Constitution, of our commitment to the rule of law and renewal of that which we inherited and hope to pass on, unbroken, unshattered," he said. "Vote for this -- for America, for our constitution, for democracy, for history."