His colleague, Rep. Ruben Gallego, D-Ariz., said Democrats would call for impeachment “when there is no longer any other recourse.”

“We are certainly moving down that path,” said Gallego, who like Pocan was speaking on a conference call organized by progressive groups. “There is a lot of runway until we get there.”

Impeachment has happened twice in American history. It requires a majority of votes in the House, after which it would be sent to the Senate. There, two-thirds of senators must vote to remove the president to force him from office.

With Republicans in control of the House and the Senate, impeachment is unlikely even if Democrats do support it. But the party’s decision to pursue it would nonetheless be significant, especially as voters decide during next year’s midterm elections whether to give control of Congress back to Democrats.

Some progressive activist groups want Democrats to take the plunge. One of them, Democracy for America, said in a note to members Tuesday that Trump’s actions were “a repeat of Richard Nixon’s most notorious actions during the Watergate scandal” and demanded impeachment. A spokesman for the group says it is the first time it has ever called for a president to be impeached. The Progressive Change Campaign Committee is polling its members now to see whether they support it.

On Wednesday afternoon, several hundred activists gathered in front of the White House, a protest ostensibly about demanding that Congress appoint a special prosecutor to investigate ties between Trump’s presidential campaign and Russia. But many of the protesters were more interested in describing Trump’s firing of Comey as a threat to the republic.

“It’s high noon, and we’re at a tipping point for our democracy,” said Ben Wikler, Washington director for MoveOn.org, which organized the rally.

The gathered protesters held signs calling for impeachment and started chants comparing Trump’s government to an autocracy. Usually, these types of activists represent the leftward fringe of discussion inside the Democratic Party, with the politically minded party leaders taking more conservative positions.

But increasingly the rhetoric from activists and party leaders is overlapping.

“This is actually worse than the Saturday night massacre,” Tom Perez, the new chairman of the Democratic National Committee, said at the rally organized by MoveOn.org. Perez was referencing former President Nixon’s infamous order in 1973 to fire an independent special prosecutor investigating Watergate.

Other Democratic leaders have called Trump’s action “Nixonian” and a “cover-up.”

After the rally, Perez told reporters that it was clear to him that former Trump National Security Adviser Michael Flynn, forced to resign in February after he was caught lying about his communication with a top Russian official, will be prosecuted. That will be only the beginning, the DNC chair said.

“When you follow the facts to where the facts lead you, I think it’s going to be clear that there was collusion between the Trump campaign and the Russian government to affect the results of this election,” Perez said. “It doesn’t take a rocket scientist to figure out why Comey got fired.”

Asked whether he was declining to support impeachment, Perez demurred.

“I’d like to know what the facts are,” he said. “And the best way to know the facts is to have an independent investigation.”