Senator Charles E. Grassley (R-Iowa), seen here in a file photo, urged the White House this week to “reconsider” the nominations of two of President Trump’s judicial nominees. (Rachel Mummey/For The Washington Post)

President Trump's aggressive push to fill scores of federal court vacancies with conservative judges hit severe turbulence this week, as he was forced to withdraw two nominees and an embarrassing video went viral showing a third struggling to answer rudimentary questions about the law.

The White House said Friday that it is standing by the nomination of Matthew Petersen, a nominee for the U.S. District Court for the District of Columbia, despite a clip from his confirmation hearing posted on Twitter in which Petersen was unable to answer questions about legal and courtroom terms posed by a Republican senator.

The episode offered more ammunition to Democrats, who have accused Trump of tapping inexperienced nominees in a rush to reshape the federal judiciary. Even some Republicans have suggested they've felt pressured by the White House to move forward with his picks.

White House spokesman Hogan Gidley defended the qualifications of Petersen, a member of the Federal Election Commission since 2008 with no trial experience, saying the regulatory panel handles "the very kinds of issues" the court decides.

"It is no surprise the President's opponents keep trying to distract from the record-setting success the President has had on judicial nominations, which includes a Supreme Court Justice and twelve outstanding circuit judges in his first year," Gidley said in a statement.

Until this week, Trump's record of getting judicial nominees confirmed by the Senate stood out as a bright spot for a president who has struggled for big wins on Capitol Hill. In addition to Supreme Court Justice Neil M. Gorsuch, the Senate has confirmed 12 circuit court judges and six district court judges.

In a news release this week, Senate Republicans touted their work with Trump as "the sleeper story of the year." But that release came just a day after the nominations for two district court judgeships began to run aground, as Republicans on the Judiciary Committee registered strong objections to the nominees' credentials and character.

This year is the first since 2006 in which the GOP has controlled both the presidency and Senate, presenting a prime opportunity to fill lifetime appointments to what are currently 143 vacancies on the federal bench.

Only one GOP senator — John Neely Kennedy of Louisiana — has voted against a Trump judicial nominee. But this week demonstrated a new willingness by Senate Judiciary Chairman Charles E. Grassley (R-Iowa) and others to derail Trump's picks.

Grassley on Tuesday told the White House to "reconsider" the nominations of Jeff Mateer and Brett Talley, both of whom were reported to have endorsed positions or groups that embrace discrimination. A day later, both nominations were pulled.

Talley, Trump's nominee for a U.S. district court seat in Alabama, originally had received the endorsement of the Judiciary Committee, despite the fact that he had never litigated a case and was one of two Trump picks whom the American Bar Association had found "not qualified" for the federal bench.

Mateer was nominated to serve on the bench in the Eastern District of Texas, but the committee never received his paperwork.

Mateer, according to reports, had said in 2015 that transgender children are part of "Satan's plan," while Talley was reported to have posted a defense of "the first KKK" in an online comment in 2011.

Neither disclosed those comments during the vetting process. Talley also did not tell the committee that he is married to the chief of staff for White House counsel Donald McGahn.

For Grassley, those transgressions were enough to yank his support. But he refused to condemn the White House for nominating Talley — or voice any concerns with its vetting process.

"There's no way to have an absolutely perfect way of vetting," Grassley said. "With all this social networking, how do you keep track of everything that everybody does?"

A Harvard Law School graduate, Tally had once belonged to a paranormal research group in Tuscaloosa, Ala., that hunted for ghosts, according to a biography submitted to the Senate. He also drew fire from critics for hard-right blog posts, some of them strongly opposing restrictions on gun ownership.

Objections by Democrats to his résumé did not initially appear to faze Republicans, who in recent weeks have instead lashed out at the ABA, accusing it of being politically biased in its rankings.

Republicans also have accused Democrats of inventing excuses to try to block qualified nominees with whom they disagree politically from ascending to the bench. This complaint is at the heart of the GOP's decision this year to waive the traditional "blue slip" consensus process — named for the piece of paper senators from a potential federal judge's state must sign to indicate their approval — in some cases where only Democrats are objecting to the consideration of circuit court judges.

A White House official acknowledged that Trump had a bad week on judicial nominations but said the president remains undeterred in following through on a campaign promise to appoint conservative judges — a pledge that is particularly important to his political base.

"Our efforts are not going to be deterred by a negative news cycle," said the official, who was not authorized to speak publicly and spoke on the condition of anonymity to be candid.

The video of Petersen that went viral Thursday captured five minutes of brutal questioning by Kennedy at Petersen's confirmation hearing the day before. It was posted on Twitter by Sen. Sheldon Whitehouse (D-R.I.), who wrote that it showed Kennedy asking Peter­sen "basic questions of law & he can't answer a single one."

"Hoo-boy," Whitehouse wrote.

During Wednesday's hearing, Kennedy started by asking Petersen, whom the ABA rated as qualified for a judgeship, and four other nominees who appeared with him, "Have any of you not tried a case to verdict in a courtroom?"

Petersen alone raised his hand. Kennedy then bore down.

Had Petersen ever handled a jury trial? "I have not," the nominee responded.

Civil? No. Criminal? No. Bench trial? No. State or federal court? No.

How many depositions had he taken — fewer than five?

"Probably somewhere in that range," Petersen said.

Had he ever argued a motion in state court? Federal court? No on both counts.

Kennedy then asked the last time Petersen had read the Federal Rules of Civil Procedure — the standards that govern civil cases in U.S. district courts.

"In my current position," Petersen stuttered, "I obviously don't need to stay as invested in those on a day-to-day basis, but I do try to keep up to speed."

The inquisition continued for a few more minutes.

Last month, Kennedy complained that the White House was trying to strong-arm nominees through the Senate without taking senators' opinions into consideration.

His complaint revolved around Kyle Duncan, Trump's choice to fill an empty seat on the U.S. Court of Appeals for the 5th Circuit. Instead of consulting him, Kennedy said, White House counsel McGahn told him in a "very firm" tone that Duncan would be the nominee, "to the point that he was on the scarce side, in one conversation, of being polite."

A spokeswoman for Kennedy said Friday that he has not decided if he will vote against Petersen's nomination. Kennedy backed out of a scheduled interview with The Post. In a statement, he defended his questioning.

"I enthusiastically supported President Trump for president, and I still do," Kennedy said. "In the past year, I have supported nearly every one of President Trump's picks, but I don't blindly support them. I ask questions that I expect them to be able to answer. In doing so, I'm just doing my job."

A statement issued by Whitehouse's office said Petersen's testimony "speaks for itself."

"Mr. Petersen has been nominated to one of the busiest courts in the country but he's never tried a case," the statement said. "He's never argued a motion. He cannot recall the basic legal procedure and doctrine he would be charged with applying."

Petersen, a graduate of the University of Virginia Law School, has served on the FEC for nearly a decade. His tenure there overlapped with that of McGahn, before he was White House counsel, for about five years.

Current and former FEC officials described Petersen as amiable, bright, well liked by his colleagues and deeply devoted to anti-regulatory principles. A study of the commission's voting patterns found that Petersen voted in virtual lockstep on key issues for years with other Republicans on the commission, including McGahn.

In an interview, Ann Ravel, a former Democratic commissioner who served with Petersen for more than three years, questioned Petersen's assertion that he gained legal experience through oversight of FEC lawyers, saying the commission had little direct responsibility for litigation, legal techniques or strategy.

"I do not believe it qualifies one to be a federal judge," said Ravel, who is now a professor at the University of California at Berkeley Law School.

Derek Hawkins contributed to this report.