WASHINGTON — Numerous House Democrats on Tuesday demanded immediate impeachment proceedings against President Trump amid White House resistance to their investigations, a marked increase in support for launching an effort to remove the president from office.

The calls came in response to former White House counsel Donald McGahn’s refusal to attend a congressional hearing, despite a House subpoena. The snub served as a final straw for several Democrats who were already leaning toward starting an impeachment inquiry.

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A name placard is displayed for former White House Counsel Don McGahn, who refused to appear before a House Judiciary Committee hearing on Tuesday. Associated Press/Patrick Semansky

There are still many Democrats – chief among them Speaker Nancy Pelosi, D-Calif. – who are reluctant to pursue impeachment, worried about the political risk of appearing too eager to oust Trump and aware that the GOP-controlled Senate is all but certain to refuse to convict Trump and remove him from office.

But the move toward impeachment Tuesday puts Pelosi in the middle of a divided House Democratic caucus. She has advocated for a cautious approach, arguing that she would only support impeachment if it is bipartisan and amid overwhelming evidence. She has called a closed-door speaker’s meeting with her members for Wednesday morning to discuss where the House’s many investigations and lawsuits stand.

Several Democrats on Tuesday came out publicly in support of an impeachment inquiry for the first time. Among them were prominent Democrats such as Reps. Mark Pocan of Wisconsin and Pramila Jayapal of Washington, co-chairs of the influential Congressional Progressive Caucus; freshman Rep. Mary Gay Scanlon of Pennsylvania, vice chair of the Judiciary Committee; and Rep. Madeleine Dean of Pennsylvania, who is also on the panel.

Rep. David Cicilline of Rhode Island, who is chairman of the Democratic Policy and Communications Committee, said Monday night that McGahn’s refusal to testify would push him to call for impeachment.

“What people have realized is it’s not just everything detailed in (special counsel Robert S. Mueller III’s) report. It’s the administration’s continuing refusal to cooperate with Congress and attempt to continue to obstruct justice,” said Rep. Diana DeGette, D-Colo., who called for impeachment proceedings Tuesday. “That’s why I think more and more people are frustrated, because we’ve never seen anything like this.”

Jayapal, who sits on the Judiciary Committee at the center of the investigations, says the support is growing among both progressives and centrists.

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Former White House counsel Don McGahn. Associated Press/Jacquelyn Martin

Democrats “are coming up to me saying: We were elected to do a job. We were sworn to uphold the Constitution,” she said. “A situation in which the president and the administration can completely – not just undermine, but actually destroy – the foundation of checks and balances is something we can’t (ignore).”

While centrists may have spoken to Jayapal privately, those who have publicly called for impeachment proceedings are, for the most part, the House’s most progressive members, those who are most likely to have long supported impeachment. “I don’t feel the numbers (of impeachment supporters) are increasing, but the megaphone is getting bigger,” said one senior Democratic aide. “The amp is going up, but the chorus is not growing.”

Pelosi’s job now will be to prevent the dam from breaking. She has forged a winding path of congressional investigations and subpoenas that may prolong a final decision on impeachment until Election Day 2020, when the president will be on the ballot and the question could be moot. Pelosi and other senior Democrats don’t want to begin impeachment proceedings unless they know it will be successful, according to Democratic aides.

But senior Democratic leaders acknowledge that it may be hard to hold lawmakers back for 18 months. There is unlikely “any Democrat who probably wouldn’t in their gut say: ‘You know, he’s done some things that probably justify impeachment,’” said House Majority Leader Steny Hoyer, D-Md. But, “this is the important thing. I think the majority of the Democrats continue to believe that we need to continue to pursue the avenue that we’ve been on, in trying to elicit information, testimony, review the Mueller report (and) review other items going on. And if the facts lead us to broader action, so be it.”

Some Democrats are worried about losing focus on the issues “we were elected to” work on – things such as health care policy, immigration reform and infrastructure, according to Rep. Scott Peters, D-Calif..

But he acknowledged that he expects Congress to pursue impeachment proceedings.

“It just wouldn’t surprise me if that’s where it ends up,” he said. “I don’t know what the alternatives are if he’s going to stick his middle finger up to Congress and pretend he’s a king.”

The House’s pace of investigations shows no sign of slowing. The Judiciary Committee on Tuesday subpoenaed former White House Communications Director Hope Hicks as well as a former White House counsel’s office aide, Annie Donaldson.

Earlier Tuesday, the panel convened to hear testimony from McGahn, who was a pivotal witness for Mueller’s team but said that he would abide by the Justice Department’s instruction to not testify before Congress.

He was directly involved in some of the most explosive incidents detailed in the Mueller report, such as Trump’s effort to fire the special counsel. McGahn prepared to resign rather than pass along Trump’s directive that Mueller needed to be removed, and he told former White House chief of staff Reince Priebus that Trump had asked him to do “crazy s–t,” according to the report.

After The New York Times revealed the incident the following year, Trump tried to persuade McGahn to release a statement disputing the report. He also wanted McGahn to write a letter “for our records” to say it wasn’t true. McGahn declined to take either step.