President Donald Trump is increasingly likely to face impeachment proceedings as House Democrats raced Tuesday to pursue allegations that he solicited foreign interference in the 2020 election.

Speaker Nancy Pelosi’s months-long effort to contain the push for impeachment has crumbled in the face of the startling new allegation of abuse of power by Trump. Pelosi is expected to make a statement on the issue Tuesday and has seemed more open to the idea of an impeachment investigation than ever before, according to lawmakers and aides.

The House is likely to take up a resolution Wednesday condemning Trump's alleged attempts to pressure Ukrainian officials to launch an investigation into former Vice President Joe Biden in return for hundreds of millions of dollars in U.S. military aid. The resolution won't call for Trump's impeachment, although it could become the basis for such proceedings.

Democrats are also considering a special committee to oversee potential impeachment proceedings, though such a move would prove divisive among Democrats already pursuing impeachment efforts.

Pelosi will face the 235-member Democratic Caucus in a closed-door meeting Tuesday afternoon that could determine whether she's prepared to put the muscle of the speakership behind impeachment proceedings after months of resistance. That will come after Pelosi huddles with the key committee chairmen leading the various Trump-related probes.

But there's no question where the momentum stands, as a throng of Democratic hold-outs endorsed an impeachment probe.

"I truly believe the time to begin impeachment proceedings against this president has come," said Rep. John Lewis (D-Ga.), a revered figure in the caucus and Pelosi ally whose blessing was seen as a signal that House leaders were on board. Lewis said after his remarks that he talked to Pelosi before announcing his decision.

By Tuesday morning, the number of Democrats publicly backing impeachment proceedings had surged to two-thirds of the caucus, with more poised to join them by the end of the week. That includes a sharply climbing number of Democrats considered vulnerable in 2020. By Tuesday afternoon, more than half of the 44 "frontline" Democrats — considered the party's most vulnerable incumbents — had voiced support for impeachment proceedings.

"Having taken an oath of office before God and my fellow citizens to support and defend the Constitution of the United states, I can only conclude that Congress move forward with articles of impeachment," said Rep. Antonio Delgado (D-N.Y.), one of those vulnerable Democrats.

Though impeachment seemed unlikely as recently as last week, Democrats were pushed to the brink amid reports that Trump used the leverage of his office to pressure Ukraine’s president to interfere in the 2020 election by investigating Biden and his son Hunter, who served on the board of a Ukrainian energy firm.

Trump has already acknowledged that on a July 25 call with Ukraine's president, Volodymyr Zelensky, he encouraged the recently elected leader to probe Biden's involvement in the ouster of a Ukrainian prosecutor who was seen by the international community as corrupt. But Trump allies have claimed with no evidence that Biden may have acted to protect Hunter Biden.

Democrats say Trump's open solicitation of assistance in the 2020 election from a foreign leader — especially one reliant on U.S. aid in an ongoing military struggle against a Russian incursion in eastern Ukraine — is a grave abuse of power. Also outraging the party: Trump has blocked a whistleblower complaint reportedly involving his actions toward Ukraine from reaching Congress, despite laws requiring it to be shared with the Intelligence Committees.

Democratic leaders now view a House Intelligence Committee hearing on Thursday featuring Trump's top intelligence official — as well as a deadline that day for the State Department to turn over related documents potentially implicating the president and his personal lawyer, Rudy Giuliani — as the deciding factor over whether to move forward with impeachment proceedings.

Pelosi has been coming under increasing pressure to embrace impeachment as freshman Democrats in swing districts rethink their stance after Trump’s alleged attempt to pressure Ukrainian officials in an effort to tarnish the former vice president, the frontrunner for the 2020 Democratic nomination.

Notably, seven Democratic freshmen from swing districts called for "impeachment hearings" in a Washington Post op-ed for what they said would be an "impeachable offense" if true.

When Pelosi speaks to Democrats on Tuesday afternoon, it will be to a caucus that is now thirsting for a more aggressive confrontation with Trump. Many more lawmakers indicated they were likely to join the call for impeachment proceedings by Thursday, when the Trump administration is expected to blow off another congressional demand for the whistleblower complaint.

The contours of a potential impeachment process are still somewhat in flux. Though the Judiciary Committee is engaged in what the panel has been calling an "impeachment investigation" for months, some Democrats have been whispering since June about the prospect of forming a new "select committee" to handle the impeachment probe.

Though there would be logistical hurdles to such a move, it would come amid grumbling in some corners of the caucus — and from Pelosi herself — that the Judiciary Committee has struggled to sustain momentum for impeachment efforts.

Judiciary Committee Democrats, meanwhile, have at times expressed frustration about the constraints they've faced from House leaders. Pelosi herself has refused to publicly characterize the committee's probe as an "impeachment investigation," snarling the House's message as members struggled to define what they were doing.

The rise of the Ukraine issue as the tipping point for impeachment efforts is a whiplash-inducing turn after Democrats failed to garner public support for such a move in the wake of special counsel Robert Mueller's report about the Trump campaign's welcoming of Russian interference in the 2016 election.

Mueller portrayed a campaign eager to benefit from Russia's malign activity and a president eager to thwart the investigation of his allies — providing evidence of potential instances of obstruction of justice.

But Mueller's report and his public testimony in late July failed to galvanize public sentiment, even as a steady stream of Democrats cited his work to endorse impeachment proceedings.

Andrew Desiderio and Sarah Ferris contributed to this report.