House Speaker Nancy Pelosi said that House Democrats will not hold a vote to authorize an impeachment inquiry into President Donald Trump – defying calls from the White House and Republicans to do so.

The decision to hold off on a formal vote comes amid growing pressure from Republican lawmakers and White House officials who have criticized House Democrats’ efforts as an illegitimate attempt to undermine Trump’s presidency. On the other hand, according to a source familiar with the matter, many members of Pelosi’s caucus want to avoid the perception that the White House is dictating how the House — as part of a separate and equal branch of government, conducts itself.

“We’re not here to call bluffs,” Pelosi said at a press conference on Tuesday 10/15. “This is not a game to us. This is deadly serious,” she said.

The impromptu press conference came just before Democratic presidential candidates were set to take the stage in the fourth debate of the 2020 primary. During the presser, Adam Schiff said that “the Constitution is very clear — The House will have the sole power of impeachment. Republicans know it, but they don’t want to discuss the president’s conduct,” Schiff added. “They’d rather discuss the process.”

Pelosi has dismissed the calls for a vote as a “Republican talking point,” and said in an interview earlier this month that “we’re certainly not going to do it because of the president.”

Though Pelosi had previously expressed little interest in holding a vote on an impeachment inquiry, Democratic leaders on Tuesday began consulting with members in moderate or pro-Trump districts to gauge their appetite for holding a formal vote, which could be uncomfortable for some. While Congress has been out of session for the last two weeks, polls show public support for the impeachment inquiry has risen. So there was some hope that a vote might be easier for some.

But several lawmakers remained opposed to a vote, saying they did not want to appear to be bowing to GOP pressure or concede to the argument that without a vote the inquiry is not legitimate.

Republicans have seized on Pelosi’s stance. Vice President Mike Pence, who had been sent a request for documents as part of the probe, on Tuesday said he would refuse to comply with the “self-proclaimed ‘impeachment inquiry,’” according to a two-page letter to Democratic House committee leaders by his counsel.