WASHINGTON (AP) — Democrats' momentum for a fresh drive to quickly impeach outgoing President Donald Trump gained support Saturday, and a top Republican said the president's role in the deadly riot at the Capitol by a violent mob of Trump supporters was worthy of rebuke.

Sen. Pat Toomey, R-Pa., said he believed Trump had committed “impeachable offenses.” But he did not explicitly say whether he would vote to remove the president from office at the conclusion of a Senate trial if the House sent over articles of impeachment.

“I don’t know what they are going to send over and one of the things that I’m concerned about, frankly, is whether the House would completely politicize something,” Toomey said Saturday on Fox News Channel, speaking of the Democratic-controlled House.

“I do think the president committed impeachable offenses, but I don’t know what is going to land on the Senate floor, if anything," Toomey said.

Late Saturday, House Speaker Nancy Pelosi sent a letter to her Democratic colleagues reiterating that Trump must be held accountable — but stopped short of committing to an impeachment vote. Still, she told her caucus, “I urge you to be prepared to return to Washington this week.”

“It is absolutely essential that those who perpetrated the assault on our democracy be held accountable,” Pelosi wrote. “There must be a recognition that this desecration was instigated by the President.”

Pelosi said House Democrats “will be proceeding with meetings with Members and Constitutional experts and others.”

The new Democratic effort to stamp Trump's presidential record — for the second time and days before his term ends — with the indelible mark of impeachment gained more supporters Saturday. Rep. David Cicilline, D-R.I, a leader of the House effort to draft impeachment articles — or charges — accusing Trump of inciting insurrection, said his group had grown to include 185 co-sponsors.

Lawmakers plan to formally introduce the proposal on Monday in the House, where articles of impeachment must originate. If Democrats decide to move forward, a vote could be possible by Wednesday — exactly one week before Democrat Joe Biden becomes president at noon on Jan. 20.

The articles, if passed by the House, could then be transmitted to the Senate for a trial, with senators acting as jurors who would ultimately vote on whether to acquit or convict Trump. If convicted, Trump would be removed from office and succeeded by the vice president.

Earlier Saturday, Pelosi told her San Francisco constituents during an online video conference that it is "a decision that we have to make.”

Potentially complicating that decision is what it means for Biden and the beginning of his presidency. While reiterating that he has long viewed Trump as unfit for office, Biden on Friday sidestepped a question about impeachment, saying what Congress does “is for them to decide.”

If the House decided to impeach, the soonest the Senate could begin an impeachment trial under the current calendar would be Jan. 20, Inauguration Day.

A violent and largely white mob of Trump supporters overpowered police, broke through security lines and rampaged through the Capitol on Wednesday, forcing lawmakers to scatter as they were putting the final, formal touches on Biden’s victory over Trump in the Electoral College.

The crowd surged to the domed symbol of American democracy following a rally near the White House, where Trump repeated his bogus claims that the election was stolen from him and urged his supporters to march in force toward the Capitol.

Five people, including a Capitol police officer, died as a result of the siege.

“It has been an epiphany for the world to see that there are people in our country led by this president, for the moment, who have chosen their whiteness over democracy,” Pelosi said of the attack.

She added: “This cannot be exaggerated. The complicity, not only the complicity, the instigation of the president of United States, must and will be addressed.”

No. 4 House Democratic leader Hakeem Jeffries of New York reiterated support for moving against what he deemed “an act of sedition that was incited and encouraged by Donald Trump.”

Speaking of Trump, Jeffries said Saturday: “He should be impeached, convicted and thrown out of 1600 Pennsylvania Avenue and forever banished to the dustbin of history."

Outrage over the attack and Trump's role in egging it on capped a divisive, chaotic presidency like few others in the nation’s history. There are less than two weeks until Trump is out of office but Democrats have made clear they don't want to wait that long.

Trump, meanwhile, has few fellow Republicans speaking out in his defense. He's become increasingly isolated, holed up in the White House as he has been abandoned in the aftermath of the riot by many aides, leading Republicans and, so far, two Cabinet members — both women.

Sen. Lisa Murkowski, R-Alaska, who has long voiced her exasperation with Trump's conduct in office, told the Anchorage Daily News on Friday that he simply “needs to get out.”

Sen. Ben Sasse, another Trump critic, said more important than what happens to Trump “is what happens to the United States people and this union 12 days and beyond.”

But the Nebraska Republican also told “CBS This Morning” on Friday that he “will definitely consider” whatever articles the House sends over because he believes Trump “has disregarded his oath of office” to preserve, protect and defend the Constitution.

After spending many weeks refusing to concede defeat in the November election, Trump promised — after the Capitol riot — to oversee a smooth transfer of power to Biden. He called for reconciliation and healing, but then announced he will not attend the inauguration — the first such presidential snub since just after the Civil War.

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Superville reported from Wilmington, Delaware. Associated Press writers Alexandra Jaffe, Lisa Mascaro, Mary Clare Jalonick and Zeke Miller contributed to this report.