MIDLAND CITY, AL - DECEMBER 11: Former White House strategist Steve Bannon speaks before Senate candidate Roy Moore at a 'Drain the Swamp' campaign rally at Jordan's Activity Barn in Midland City, AL on Monday, Dec. 11, 2017. (Jabin Botsford/The Washington Post)

The House Intelligence Committee is preparing for a showdown with former White House strategist Stephen K. Bannon that members call a moment of truth for Congress if it wants to maintain any authority to scrutinize the Trump administration.

Panel lawmakers are urging leaders to issue a contempt citation for Bannon if he refuses to answer their questions during an interview expected Thursday — their second attempt to compel Bannon’s testimony in recent weeks. Lawmakers subpoenaed him last month when he declined to address subjects related to their probe of Russian meddling in the 2016 presidential election.

Bannon has successfully delayed several attempts to reschedule the interview while his lawyers coordinate with the administration, and according to members of the committee, he still maintains he will not answer questions about his time on Trump’s transition team or in the White House.

A lawyer for Bannon didn’t respond to requests for comment.

Democrats and Republicans say they must issue a contempt citation if Bannon continues to avoid them.

“If you don’t, I mean, what kind of precedent is that sending? For not just our committee, but every committee?” said Rep. Thomas J. Rooney (R-Fla.), who was deputized to help run the committee’s Russia probe. He surmised that the panel’s leaders, including its chairman, Rep. Devin Nunes (R-Calif.), would have to sign off on such a drastic move.

Preserving Congress’s authority to credibly compel witness testimony is paramount, Rooney said, stressing that accepting more excuses from Bannon would be acknowledging that congressional subpoenas “don’t mean anything, it’s just a hollow threat.”

“You can’t do that,” he concluded.

In his standoff with the House Intelligence Committee, Bannon has done what no other witness in the Russia probe could: unite Republicans and Democrats on the politically fractured panel.

The two sides are locked in a fundamental battle over when and where one branch of the federal government must defer to the other — and who wins could have implications for how effectively Congress is able to carry out its oversight functions, regardless of what administration controls the White House.

The dispute began during Bannon’s first attempt at closed-door testimony with the panel last month, as he refused to answer any questions related to his time on the transition team or in the administration.

Bannon’s team said they were caught off guard, according to members and others familiar with the testimony, as they thought they had struck a deal with a majority committee staffer that certain topics would be off-limits.

But neither Republicans nor Democrats questioning Bannon had agreed to an interview on limited terms, and they were not inclined to abide by such restrictions. According to multiple people familiar with the interview, Rep. Trey Gowdy (R-S.C.) led the effort to subpoena Bannon when he claimed the president might want to invoke executive privilege.

According to people familiar with the matter, Bannon’s lawyers debated with the committee over various points of legal precedent, including U.S. v. Nixon, the Supreme Court case that famously limited executive privilege.

In the past several weeks, the House counsel has taken responsibility for negotiating the terms of Bannon’s interview. As of last week, his lawyers were proposing he answer only 14 yes-or-no questions — something committee members rejected.

To date, members said, President Trump has still not made any formal claim of executive privilege over Bannon’s testimony.

“From my point of view, the only basis for Mr. Bannon to refuse to answer questions is if the executive asserts privilege, which they have not done,” the intelligence panel’s top Democrat, Rep. Adam B. Schiff (Calif.), said Wednesday.

Bannon has not expressed the same unwillingness to speak with special counsel Robert S. Mueller III, who is leading the Justice Department’s investigation into Russia’s meddling in the election and whether anyone in the Trump campaign coordinated with the Kremlin. The intelligence panel is not supposed to overlap with Mueller’s probe.

Panel members stressed, however, that the same events and people could be relevant to both investigations. But they were unsure whether Bannon would open up to the committee once his interview with Mueller is complete. Bannon was expected to meet with Mueller this week, according to a person familiar with the ­matter.

Rosalind S. Helderman and Josh Dawsey contributed to this report.