Democratic leaders are facing increasing pressure to respond to calls to impeach President Trump, as nearly a majority of House Democrats now support an impeachment inquiry.

The growing momentum comes as the first ad featuring clips from the testimony of former special counsel Robert S. Mueller III is being broadcast on televisions across the country.

“As much as this president and his administration attempt to cover up the facts, with this ad we are ensuring that Americans hear the facts directly from Mueller,” Nathaly Arriola, executive director of Need to Impeach, said in a statement Tuesday.

The organization, founded by billionaire activist Tom Steyer, said it is spending six figures on the ad, which will run on CNN and MSNBC before and after the Democratic debates on Tuesday and Wednesday night. Steyer, who spurned a presidential bid earlier this year, stepped down from the group after announcing this monththat he would seek the Democratic presidential nomination. He did not qualify to participate in this week’s debates.

Mueller’s testimony last week before the House Judiciary and Intelligence committees was largely composed of terse answers to lawmakers’ questions, prompting hand-wringing among some Democrats who worried that it would be of little help in their quest to rally public support for Trump’s impeachment.

But despite what many have described as a lackluster performance, Mueller’s testimony appears to have provided the impetus for a number of fence-sitting Democrats to join in calling for the opening of an impeachment inquiry.

According to a Washington Post tally, 114 House Democrats now say they support at least opening an impeachment inquiry into whether Trump committed “high crimes and misdemeanors.” That represents more than 48 percent of the 235-member House Democratic caucus. Rep. Justin Amash (I-Mich.), who recently left the Republican Party, has also said he supports beginning impeachment proceedings against Trump.

Seventy-seven House Democrats have joined calls for an inquiry over the past two months, 21 of them since last week in the run-up to Mueller’s testimony.

The latest came Tuesday evening, when Democratic Reps. Jennifer Wexton (Va.), Grace Meng (N.Y.), Eliot Engel (N.Y.), Jason Crow (Colo.) and Judy Chu (Calif.) announced their support for an inquiry.

Engel, chairman of the House Foreign Affairs Committee, said in a statement that Mueller’s testimony “provided ample evidence that the president committed obstruction of justice.”

“The president abused the power of his office in an effort to stymie a legitimate investigation into his campaign’s involvement with Russia,” Engel said, adding: “The American people want, and deserve, the truth.”

Wexton cited Trump’s “efforts to undermine our democratic institutions, his flagrant disregard of lawful congressional oversight, and his normalizing of authoritarian tactics.”

Meng described an impeachment inquiry as a means of gathering more information about Trump’s actions rather than an end in itself. “It is a process by which to uncover the truth, and to obstain critical supporting evidence like the grand jury materials and witness testimonies,” she said.

Crow said Congress “must complete the work started by Special Counsel Robert Mueller,” and Chu contended that an inquiry is warranted because Trump “repeatedly attempted to obstruct the federal investigation” into Russian interference.

Del. Eleanor Holmes Norton (D), the District’s nonvoting House delegate, also on Tuesday came out in favor of an inquiry, although she cautioned that lawmakers “must not allow impeachment to consume all the oxygen from the people’s agenda.”

Several of the Democrats calling for an impeachment inquiry in the wake of the Mueller hearings cited the issue of election security as a reason for their decision.

Republicans, led by Senate Majority Leader Mitch McConnell (Ky.), blocked election security bills the same week that Mueller warned that Russia was continuing to interfere in U.S. elections. Rep. Katherine M. Clark (D-Mass.), the vice-chairwoman of the House Democratic caucus, said that she was “truly stunned” by the move.

“We can’t allow Republican inaction to prop the door open for thieves to steal an election,” she said in a statement last week.

House Speaker Nancy Pelosi (D-Calif.) and other party leaders have resisted calls by rank-and-file members to open an inquiry, arguing instead that Democrats should continue pursuing investigations into Trump in Congress and the courts, particularly as the Republican-controlled Senate is unlikely to vote to convict Trump and force him out of office.

A Pelosi spokesman did not respond to a request for comment Tuesday on what the speaker plans to do if a majority of her caucus comes out in favor of an impeachment inquiry. The House is in recess until Sept. 9.

House Judiciary Committee Chairman Jerrold Nadler (D-N.Y.), whose panel has the power to launch impeachment proceedings, said Sunday that Trump “richly deserves impeachment” and has “violated the law six ways from Sunday.”

“But that’s not the question,” he added. “The question is, can we develop enough evidence to put before the American people?”

The 30-second Need to Impeach ad running Tuesday and Wednesday nights features excerpts of Mueller answering lawmakers’ questions about his report into Russian interference in the 2016 election.

In one exchange, Mueller affirms to Nadler that, contrary to Trump’s claims, he did not “totally exonerate” the president.

In another, Mueller tells Rep. Ken Buck (R-Colo.) that Trump could be charged with obstruction of justice after he leaves the White House.

In the ad’s final clip, House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) asks Mueller whether Trump’s 2016 campaign welcomed help from Russia. Mueller replies that they did.

“And then they lied to cover it up,” Schiff says.

Mueller responds: “Generally, that’s true.”

JM Rieger and Karoun Demirjian contributed to this report.