No one on Capitol Hill has yet seen the potentially explosive complaint involving President Trump that an anonymous whistleblower is trying to show lawmakers.

But in the span of less than 48 hours, it’s become the focal point of House Democrats’ ongoing impeachment drama—with some pro-impeachment lawmakers casting it as a do-or-die moment for holding Trump accountable and, more glaringly, protecting constitutional bedrocks.

“If any of these allegations are true, these are probably the most serious allegations against the president,” said Rep. Ro Khanna (D-CA), an impeachment supporter. “I do think this is going to probably move more of the members to start calling for that [impeachment] hearing… My guess is, those numbers are going to continue to go up.”

Several reports have indicated that the whistleblower’s complaint focuses on a call that Trump had in July with the newly elected Ukrainian president, Volodymyr Zelensky, in which Trump urged him to investigate the business dealings of Joe Biden’s son, Hunter, in the country. Trump lawyer Rudy Giuliani had already pushed Zelensky to open such an investigation and has admitted to as much in recent interviews.

The full content of the whistleblower’s complaint had been blocked from lawmakers by Trump’s acting Director of National Intelligence—despite it being an “urgent” matter that legally mandates congressional notification. And the stream of news suggesting Trump pressured a foreign government to conduct investigations beneficial to his 2020 re-election campaign, with the possible threat of security aid withdrawal, has fired up House Democrats who are in favor of impeachment.

“Colleagues in Congress: if this isn't impeachable abuse of power, what is?” asked Rep. Jared Huffman (D-CA) on Twitter Friday afternoon. “I'm sick of the parsing, dithering & political overcalculating.”

A Democratic aide, speaking anonymously to discuss the mood in the caucus, put it even more bluntly. “I don’t know why the hell any of us are here if we’re not going to impeach him for this,” the aide said. “Trump has no reason to change, because we won’t make him.”

But it remains the case that only Speaker Nancy Pelosi (D-CA) will decide whether the caucus moves forward with impeachment. On Friday afternoon, she called on the Trump administration to end the stonewalling on the whistleblower complaint—and promised that her committees will move to get it if they do not comply. But, notably, she did not broach the topic of impeachment.

“Reports of a reliable whistleblower complaint regarding the President’s communications with a foreign leader raise grave, urgent concerns for our national security,” she said.

The comments sparked renewed frustration among the ranks of lawmakers worried that the failure to begin impeachment proceedings has effectively abetted more ethically-dubious activity from Trump.

“She’s still holding back,” one pro-impeachment lawmaker said of Pelosi. “If impeachment isn’t for this, why is impeachment in the constitution?”

Privately, lawmakers put the tally on those who support impeachment at just under 140 members of the House. But that number has been steadily growing over the course of the summer even as Pelosi has said she sees no political upside in its pursuit.

One top Democratic party operative who has pushed impeachment in private briefings with lawmakers said he suspected Pelosi actually wanted to have her hand forced by her caucus. “That's why I don't think it is an act of disloyalty for Dems to put pressure on her,” the person said. “She wants them to do it so it is politically safe for if she does it.”

Others are doubtful that many more Democrats will move on impeachment unless or until Pelosi comes out for it. “She’s the linchpin,” said the House Democratic aide.

A leading activist group hoping to build public support for impeachment told The Daily Beast they are talking about incorporating the whistleblower news into their pressure campaign. “My question to Democrats, Republicans, and the Speaker is, what are you waiting for?” asked Kevin Mack, chief strategist for Need to Impeach.

One subject of increasing speculation on and off the Hill is whether there was an individual lawmaker of such stature that he or she could change the tenor of the impeachment debate—and force Pelosi’s hand—by coming out for it. The parallel was made to former Rep. Jack Murtha (D-PA) coming out against the Iraq War relatively soon after it started—a moment that Pelosi herself has credited with changing the tide of public opinion against the war.

But the conclusion is that few such lawmakers carry that type of weight anymore. And the names often discussed—longtime civil rights icon Rep. John Lewis (D-GA) and former President Barack Obama—would have a profound effect on fellow Democrats. But Obama is almost certain to not weigh in on the matter. And even if he did, neither he nor Lewis’ impact would likely reach beyond party lines.

“There just aren't those types of figures any more,” the Democratic operative said.