For weeks after the 2020 election had been called, Peter Navarro, a White House adviser to President Donald J. Trump, worked closely with other senior aides to keep Mr. Trump in power for a second term.

After being subpoenaed last year by the House committee investigating the Jan. 6, 2021, riot, which sought to learn more about those efforts, Mr. Navarro refused to comply, insisting that Mr. Trump had directed him not to cooperate and dismissing the subpoena as “illegal” and “unenforceable.”

Now, after more than a year of legal wrangling, Mr. Navarro, 74, will defend those claims in a trial that starts Tuesday, when jury selection is expected to begin in Federal District Court in Washington. The case centers on a relatively simple question: whether he showed contempt for Congress in defying the House committee’s request for documents and testimony.

The trial itself may be relatively short, and if Mr. Navarro were to be convicted on the two counts of contempt of Congress he is charged with, he could face up to a year in jail and a fine of up to $100,000 for each count.

Since Mr. Navarro was indicted in June of last year, he has maintained that he is protected by the former president’s claim of executive privilege.

Prosecutors intend to argue that Mr. Navarro refused of his own volition and that neither Mr. Trump nor his lawyers have confirmed whether Mr. Navarro sought or received his approval.

The judge in the case, Amit P. Mehta, has already dealt a blow to Mr. Navarro, ruling that he cannot rely on executive privilege as a pillar of his defense. He refused to dismiss the case after concluding that Mr. Navarro had failed to produce convincing evidence that he and Mr. Trump ever discussed his response to Congress.

Describing Mr. Navarro’s defense as “pretty weak sauce,” Judge Mehta emphasized that he had presented no written communications or even a “smoke signal” that would bolster his contention.

“I still don’t know what the president said,” Judge Mehta said. “I don’t have any words from the former president.”

“I don’t think anyone would disagree that we wish there was more here from President Trump,” Mr. Navarro’s lawyer, Stanley Woodward Jr., replied.

Still, outside of court, Mr. Navarro has continued to frame the case as a fundamental dispute between the legislative and executive branches, calling the fight over executive privilege “open questions” in the law and pledging to appeal.

Mr. Navarro is one of two Trump aides to face criminal charges after the House committee’s investigation. Stephen K. Bannon, another of Mr. Trump’s senior advisers, was convicted last summer on two counts of contempt of Congress and sentenced to four months in prison.

After the 2020 election, Mr. Bannon and Mr. Navarro concocted a plan, known as the Green Bay Sweep, aimed at delaying certification of the outcome of the election. The strategy involved persuading Republican lawmakers to halt the counting of Electoral College votes on Jan. 6 by repeatedly challenging the results in various swing states.

When the House committee investigating the Jan. 6 attack issued a subpoena, Mr. Bannon similarly refused to comply.

Others in Mr. Trump’s inner circle were less combative in resisting the panel’s efforts.

Two of Mr. Trump’s advisers, Roger J. Stone Jr. and Michael T. Flynn, ultimately appeared before the committee but declined to answer most of its questions by citing their Fifth Amendment rights against self-incrimination. Mr. Trump’s final chief of staff, Mark Meadows, and his deputy, Dan Scavino, negotiated the terms of their responses to subpoenas, providing documents but not testimony. None of the four men faced criminal charges.

The filing of charges against Mr. Navarro was widely seen as proof that the Justice Department was willing to act aggressively against one of Mr. Trump’s top allies as the House scrutinized the actions of the former president and his advisers and aides in the events leading up to and during the Capitol attack.

The trial could also shed new light on Mr. Navarro’s communications with the White House at key moments during Mr. Trump’s final days in power.

One possible witness for the defense is Liz Harrington, a communication aide for Mr. Trump who helped spread false claims of election irregularities in the months after the 2020 election. Ms. Harrington had been set to testify last week about Mr. Navarro’s claims of executive privilege, but could instead provide written testimony about the extent of Mr. Navarro’s contact with Mr. Trump and his aides.

Alan Feuer contributed reporting.