President Trump faces mounting pressure for his immediate ouster after he incited Wednesday’s violent siege at the Capitol — an increasingly louder drumbeat chastising his actions that threatens not only to prematurely end his waning tenure but to put him in legal jeopardy once he leaves office.

In Congress, a growing cadre of House Democrats is pushing to rapidly impeach Trump a second time before he is scheduled to leave office on Jan. 20. They are preparing to introduce articles charging him with inciting an insurrection and having “gravely endangered the security of the United States” and its institutions.

In public, Trump has come as close as he is likely to get to admitting he lost the election, acknowledging that there will be a transfer of power and confirming Friday that he will not attend President-elect Joe Biden’s inauguration. But in private, the president has tried to rationalize his actions, saying he wanted only to encourage a large protest that would garner news coverage and rattle members of Congress — not for his supporters to actually storm the Capitol in the worst breach of its security since the War of 1812.

Following the Jan. 6 pro-Trump mob that breached the Capitol, politicians began calling for invoking the 25th Amendment or the impeachment of President Trump. (The Washington Post)

Legal advisers to the president and his allies expressed increasing concern Friday about possible criminal liability in the wake of Wednesday’s melee, according to a person familiar with the conversations. Trump has been told by attorneys that he could face legal jeopardy for inciting a mob; he has responded that it was never his intent to do so, according to a separate close adviser, who like others spoke on the condition of anonymity to disclose internal discussions surrounding the president.

Meanwhile, Senate Republicans who declined an opportunity to evict Trump from office last year are rapidly turning against him — pledging to entertain whatever impeachment charges the House may send and, in the case of one prominent senator, demanding his immediate resignation.

“I want him out. He has caused enough damage,” Sen. Lisa Murkowski (R-Alaska) said in an ­interview with the Anchorage Daily News published Friday. “He’s either been golfing or he’s been inside the Oval Office fuming and throwing every single person who has been loyal and faithful to him under the bus, starting with the vice president.”

Still, removing Trump by the one means available to Congress is a tall order in the days remaining in his presidency. House Speaker Nancy Pelosi (D-Calif.) has not made a formal determination to move forward with a second impeachment, even as she consulted Friday with the chairman of the Joint Chiefs of Staff about curbing Trump’s ability to launch nuclear weapons. Trump was previously impeached by the Democratic-controlled House for seeking to pressure Ukraine to dig up dirt on Biden; he was later acquitted by the GOP-controlled Senate.

In a letter to Democratic lawmakers, Pelosi described speaking to the Joint Chiefs chairman, Gen. Mark A. Milley, “to discuss available precautions for preventing an unstable president from initiating military hostilities or accessing the launch codes and ordering a nuclear strike.” She further described Trump as “unhinged” and said lawmakers “must do everything that we can” to protect the nation from him.

In a statement Friday evening, Pelosi reiterated that she and other House Democrats hope Trump will resign. But if he doesn’t, the House will move forward with legislation drafted by Rep. Jamie Raskin (D-Md.) that will create a commission on presidential disabilities to prepare for action under the 25th Amendment, as well as a motion for impeachment.

“With great respect, our deliberations will continue,” she said.

Biden declined to say outright Friday whether he supported Trump’s impeachment. But he did not appear to have much appetite to engage in a political fracas that would be almost certain to consume the first days of his presidency later this month.

“If we were six months out, we should be moving everything to get him out of office — impeaching him again, trying to invoke the 25th Amendment, whatever it took to get him out of office,” Biden told reporters during a news conference in Wilmington, Del. “But I am focused now on us taking control as president and vice president on the 20th and get our agenda moving as quickly as we can.”

Yet outrage over Wednesday’s events has grown to the point that it could be impossible for Pelosi and other leaders in the party to ignore, prompting a vote as soon as early next week, according to interviews with House Democratic members and aides.

House Majority Whip James E. Clyburn (D-S.C.) said in an MSNBC interview after the conference call Friday that “the sentiment of the caucus is moving” toward impeachment: “The American people have seen enough, and they are ready for us to do the job of impeaching this man.”

Some White House aides have started to discuss an impeachment scenario, although no formal team or plan has been put in place because the counsel’s office believes there won’t be adequate time, according to a senior administration official. Trump and advisers, including senior adviser and presidential son-in-law Jared Kushner, tried Friday to rally political support against impeachment, calling allies to ask them to argue against it.

Still, one top adviser counseled Trump on Friday that Democrats were going to overreach with impeachment, and that if they want to turn Wednesday’s events into a partisan battle, that is a good fight for the president to have.

Treasury Secretary Steven Mnuchin has been personally involved in discussions about invoking the 25th Amendment, a constitutional provision that provides procedures for removal of a president. But he is unlikely to pursue the option, which can be invoked by the vice president and half the Cabinet, according to three people aware of the treasury secretary’s remarks.

No Republican House members have indicated that they would back impeachment, and the top House Republican, Rep. Kevin McCarthy (Calif.), warned Democrats against proceeding.

But Rep. Adam Kinzinger (R-Ill.) has called on Vice President Pence to invoke the 25th Amendment and remove Trump. Others have suggested that they would welcome Trump’s resignation or his removal under those circumstances, while Sen. Ben Sasse (R-Neb.) told “CBS This Morning” on Friday that he could “consider” any impeachment articles forwarded by the House.

While House Democrats could impeach Trump on their own, removing him would require a two-thirds vote of the Senate — meaning 17 Republicans would have to join with the 50 Democrats who will be seated once Sens.-elect Jon Ossoff and Raphael Warnock are certified as the winners of Tuesday’s Georgia runoffs.

Senate impeachment trials are governed by an intricate and lengthy set of procedures that could be difficult to waive. Trump’s first impeachment trial, which concluded in February, lasted 20 days.

Trump could still be impeached after he leaves office, most constitutional scholars say, which would have the effect of barring him from the presidency again.

But there is a political barrier to proceeding with a Senate trial: the impending inauguration of Biden, and his need to rapidly confirm a Cabinet. Senate Majority Leader Mitch McConnell (R-Ky.) made that case in a memo circulated among GOP colleagues late Friday that outlined how it would be virtually impossible for the Senate to take up articles of impeachment before Jan. 19.

Trump tweeted Friday that he would not be present for Biden’s inauguration and, in a separate tweet, vowed that his political movement will continue.

“The 75,000,000 great American Patriots who voted for me, AMERICA FIRST, and MAKE AMERICA GREAT AGAIN, will have a GIANT VOICE long into the future,” he tweeted. “They will not be disrespected or treated unfairly in any way, shape or form!!!”

Twitter permanently banned Trump’s account later Friday, citing “the risk of further incitement of violence.”

Aides said they were trying to get Trump to do “usual government work” next week during his last days in office, such as updates on a coronavirus vaccine, the rebuilding of the military, the border wall and the economy. They are trying to plan events hoping he will attend. “We are trying to get him to do it,” the official said. “It’s being worked on.”

But on Friday, there was also increased discussion of the potential liability the president and others could face following the death of a federal officer during the riot at the Capitol.

Federal and local law enforcement agencies seek to question protesters about whether they stormed the Capitol because the president and top allies directed them to do so, according to people familiar with the discussions. D.C. Attorney General Karl A. Racine, in a Friday interview on “Good Morning America,” asked that anyone with information about the “mobsters” who assaulted the Capitol call his office and the federal prosecutors in the U.S. attorney’s office.

He said his investigation will include those who incited the attack.

“I know this. More people died at the Capitol of the United States than in Benghazi,” Racine said, referring to the 2012 attacks on U.S. facilities in the eastern Libyan city. “Donald Trump Jr., Rudy Giuliani and even the president of the United States were calling on their supporters and hate groups to go to the Capitol and, in Rudy Giuliani’s words, exercise combat justice. We’re going to investigate not only those mobsters but those who incited the violence.”

But later Friday, asked about the possibility that Trump or other speakers who addressed the president’s supporters at a rally near the White House on Wednesday could face charges for inciting violence, Kenneth Kohl, the No. 2 prosecutor in the U.S. attorney’s office in Washington, said, “We don’t expect any charges of that nature.”

Federal and D.C. laws make it illegal to “incite a riot” or “incite violence.” Compounding the matter further, experts said, is that a Capitol Police officer was killed in the insurrection.

‘‘The death of a federal law enforcement officer changes everything,” said Steve Ryan, a defense lawyer and former federal prosecutor. “It is possible that those who invaded the Capitol thinking they might get a minor misdemeanor are now theoretically subject to murder and felony murder charges.’’

The president has discussed pardoning himself, but no formal papers have been drawn up, according to person familiar with the matter, and he has given no orders to draw them up. Another close adviser to Trump said there also have been discussions about preemptive pardons for top White House aides who have been in the closest proximity to the president.

The official who would be in charge of overseeing the pardon effort — White House Counsel Pat Cipollone — was himself considering resigning, although he has been flooded with calls from Republican senators urging him to stay put, according to people familiar with the matter.

Various legal experts believe the president cannot pardon himself. A conservative former federal judge, J. Michael Luttig, wrote in a Washington Post opinion piece last month that Trump cannot do so. A self-pardon, he wrote, “would grievously offend the animating constitutional principle that no man, not even the president, is above and beyond the law.”

“There is a strong view among legal scholars, Justice Department veterans and my organization that the president does not have the power to pardon himself,” said Kristy Parker, a former Justice Department prosecutor who now serves as counsel at the organization Protect Democracy.

Parker said Trump “might want to think twice about taking that route” because it could make it more likely that the Justice Department would bring charges, doing so in part as a way to contest the idea that the president has the power to pardon himself.

Ashley Parker, Carol D. Leonnig and Philip Rucker contributed to this report.