Senate Democrats on Tuesday pressed President Trump's pick for an appellate court in Washington about his role as a White House lawyer in a series of legal controversies and about whether he could make judicial decisions independent of the man who nominated him.

In nine months as a deputy White House counsel, Gregory G. Katsas told senators considering his nomination that he advised the Trump administration on the travel ban on residents of certain majority-Muslim countries, ending protections for young undocumented immigrants and the Presidential Advisory Commission on Election Integrity.

Katsas, a former high-level Justice Department official and law clerk to Supreme Court Justice Clarence Thomas, sought to assure the Senate Judiciary Committee that he would recuse himself from any cases involving his work as a government lawyer. The role of a judge, he said, is to "apply the law neutrally and fairly without regard" to the views of the president behind a nomination.

The hearing Tuesday comes as Senate Majority Leader Mitch McConnell (R-Ky.) is intensifying efforts to install conservative jurists on the federal bench, as political pressures mount on the Republican Party to show more concrete achievements after months of struggling to govern. With no major legislative accomplishments despite controlling both chambers of Congress and the White House, Republican leaders have begun to worry about a backlash from its base in next year's midterms.

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If confirmed by the Senate, Katsas, 53, would join what is often referred to as the nation's second-highest court in part because the U.S. Court of Appeals for the D.C. Circuit often rules on high-profile political cases involving executive power and government regulations.

In the nearly two-hour hearing, Katsas acknowledged giving "legal advice on a few discreet questions" arising from special counsel Robert S. Mueller III's investigation into Russia's meddling in the 2016 election. He declined, when asked by Sen. Dianne Feinstein (D-Calif.), to provide any details because of concerns, he said, about undermining Mueller's probe and violating attorney-client confidences.

Republicans, including Sens. Orrin G. Hatch (Utah) and Ted Cruz (Tex.), praised Katsas for his intellect and integrity, and for representing clients without regard to political party.

McConnell has faced pressure from conservative activists to ramp up his efforts on judicial nominations. Lately, he has been advocating against observing a long-standing Senate tradition of allowing senators a chance to block judicial nominees who would have jurisdiction over their states. The "blue slips" have become a focal point on Capitol Hill in recent days.

That process doesn't exist, however, for nominees to the D.C. Circuit like Katsas, a Virginia resident, because the District has no senators of its own.

It is not typical for a president to reach into his own White House Counsel's Office to fill vacancies on a federal appellate bench in part because of questions inevitably raised about the nominee's legal advice. President George W. Bush's nomination of current D.C. Circuit Judge Brett M. Kavanaugh was stalled for three years in part because of Kavanaugh's work as a top White House aide.and ties to Republican politics

When asked Tuesday by Sen. Christopher A. Coons (D-Del.) about Trump's pardon of former Maricopa County, Ariz., sheriff Joe Arpaio, Katsas responded, "I couldn't publicly criticize my client in order to advance my personal interests today."

Nan Aron of the Alliance for Justice, a critic of Trump's judicial nominees, said Katsas's testimony "did nothing to reassure senators or the American people that as a federal judge he would act as an independent check on the out-of-control schemes of the executive branch."

Katsas has the support of many attorneys in Washington's legal establishment, including lawyers who worked with him during his stint at the Justice Department during the administration of George W. Bush. In that role, he often took an expansive view of executive power on national security policies after the Sept. 11, 2001, terrorist attacks.

Carrie Severino, chief counsel of the Judicial Crisis Network, called Katsas "seasoned and well respected" and said in a statement that he would uphold the Constitution and apply the law fairly. She called for a "speedy confirmation."

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Katsas is known for being quirky and unassuming despite his legal pedigree. He graduated from Harvard Law School and clerked for Thomas both at the high court and at the D.C. Circuit. He has argued more than 75 appeals, three at the Supreme Court, including in one of the challenges to the Affordable Care Act.

A longtime member of the conservative Federalist Society, Katsas would replace another conservative retired judge, Janice Rogers Brown, whose opinions were often infused with a libertarian streak. He would join a bench with four judges nominated by President Barack Obama and three others nominated by Democratic presidents.

Even though Katsas repeatedly refused to detail the substance of his White House legal advice, he did provide some insight into the challenge of working for Trump in the early months.

The president, he said in response to a question from Sen. Al Franken (D-Minn.), was "extremely high energy, he had made a series of campaign promises and he demands results from people who work for him."