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

Biden outlined the major points of his rescue plan: a $1.9 trillion proposal that includes a nationwide vaccination program, $1,400 checks for individuals, an extension and expansion of unemployment benefits and help for struggling communities and businesses.

Biden placed particular emphasis on housing and food insecurity and spoke about expanding SNAP benefits. He said his policy plan would extend the eviction and foreclosure moratorium, potentially previewing an executive action we could see next week. He also asked Congress to appropriate funds for rental assistance.

Biden, who preached bipartisanship while on the trail, said both he and Vice President-elect Harris had spoken with officials, mayors, and governors of both parties on a regular basis to address the problems across the country.

The president-elect also emphasized his plan's focus on helping small businesses and minority-owned businesses in particular, criticizing the Trump administration's initial approach which he said favored the wealthy and well-connected.

"Last week, I laid out how we'll make sure that our emergency small business relief is distributed swiftly and equitably, unlike the first time around. We're going to focus on small businesses, on Main Street. We'll focus on minority-owned small businesses, women-owned small businesses, and finally having equal access to the resources they need to reopen and to rebuild," Biden said.

He also pushed his plan for a mandatory federal minimum wage of $15 an hour.

"People tell me that's going to be hard to pass. Florida just passed it, as divided as that state is, they just passed it. The rest of the country is ready to move as well," he said. "No one working 40 hours a week should live below the poverty line. And that's what it means. If you work for less than $15 an hour and work 40 hours a week, you're living in poverty."

He frankly noted the "bold, practical" policy he was putting forward did not come cheap but argued there was no option to act.

"I know what I just described does not come cheaply. But failure to do so will cost us dearly," he said. "The consensus among leading economists is we simply cannot afford not to do what I'm proposing."

Biden ended his remarks with a call for unity and optimism, referencing his inauguration on Wednesday as a "new chapter for the country."

-ABC News' John Verhovek, Molly Nagle, Averi Harper and Beatrice Peterson