Peter Navarro, a trade adviser to former President Donald J. Trump, reported to federal prison in Miami on Tuesday, becoming the first senior Trump administration official to serve time over his role in the effort to subvert the results of the 2020 election.
Mr. Navarro, 74, who helped engineer Mr. Trump’s plans to stay in power after his electoral defeat in November 2020, was sentenced to four months in prison in January for contempt of Congress after defying a subpoena from the House select committee investigating the Jan. 6 riot.
At a hastily organized news conference shortly before he was set to check into the Federal Correctional Institution in Miami, a low-security prison next to the Miami-Dade zoo, Mr. Navarro reprised familiar denunciations of the Justice Department and the Biden administration.
Speaking in the parking lot of a commercial plaza, flanked by a pizza store and a pawnshop, he cast blame on the federal trial judge in his case, as well as Mr. Biden and a long list of politicians he said were motivated by hostility toward Mr. Trump.
He added that the “tragedy” of his situation was that he was likely to complete his sentence as he continues to appeal his conviction.
“I’m afraid of only one thing,” he told reporters. “I’m afraid for my country, because this — what they are doing — will have a chilling effect on every American, regardless of their party.”
Sam Mangel, a federal prison consultant who helped Mr. Navarro prepare for his surrender, said he was working to get Mr. Navarro into a unit devised for inmates over age 60 in a minimum-security satellite camp in the prison.
Inmates there share bunks in an open 80-bed dormitory with minimal privacy, Mr. Mangel said, adding that, given his age, Mr. Navarro hoped to fulfill his prison work requirements through a job as a law library clerk or another low-intensity position.
The rambling speech, delivered outside a strip mall, was a characteristically peculiar finale for Mr. Navarro, whose bravado and idiosyncrasies have been a hallmark of his career.
Mr. Navarro, a Harvard-trained economist, was a strident critic of China who helped inform Mr. Trump’s protectionist trade policies.
Before joining the Trump administration, Mr. Navarro drifted in and out of political parties, seeking office as a Democrat in California but repeatedly falling short.
In 1992, running on an environmental platform, Mr. Navarro nearly won the San Diego mayoral election, employing stunts such as swimming a mile to a campaign event where he addressed a crowd in a Speedo. He was a speaker at the 1996 Democratic National Convention, stumping for President Bill Clinton.
Mr. Navarro also turned to academia, spending more than two decades as a professor at the University of California, Irvine. While on faculty, he quoted a fictional alter ego in his books, often referred to as the Dark Prince of Disaster, to inject scathing descriptions of China.
The start of Mr. Navarro’s prison sentence brought an end to a prolonged legal challenge that finished at the Supreme Court on Monday as he sought to remain free while he appealed his conviction.
Mr. Navarro had argued that as a former adviser working on the president’s behalf, his case presented novel legal questions about the separation of powers and the scope of executive privilege.
But judges were unswayed.
The outcome was a marked contrast to that of another former Trump aide, Stephen K. Bannon, who was sentenced to an identical term on parallel charges but was allowed to remain free by the federal judge presiding over his case.
The House committee sought to interview Mr. Navarro in part because he, along with Mr. Bannon, devised a strategy to enlist Republican allies in Congress to delay the certification of the election by repeatedly challenging electoral vote counts in battleground states. Mr. Navarro openly discussed the plan, nicknamed the Green Bay Sweep, in a memoir and in interviews.
But when the committee asked for his testimony and documents from that period, Mr. Navarro refused to engage.
During his trial, Mr. Navarro’s lawyers contended that he had operated under a belief that Mr. Trump had asserted executive privilege and expected him not to cooperate.
But Mr. Navarro’s lawyers could point to little evidence that Mr. Trump had given instructions to that effect.
A lawyer for Mr. Navarro declined to comment on the appeal.
According to the Congressional Research Service, criminal enforcement of a congressional subpoena is exceedingly rare. And as in Mr. Navarro’s case, prosecutions still often fall short of securing Congress access to the information sought, particularly in cases involving the executive branch.
A separate civil lawsuit brought by the Justice Department is underway, in which prosecutors have sought to recover hundreds of pages of presidential records Mr. Navarro declined to provide to the National Archives and Records Administration after leaving office.
The detention of Mr. Navarro stood apart from the experience of other allies of the former president who have faced legal jeopardy but ultimately few consequences.
Mr. Trump’s longtime friend and adviser Roger J. Stone Jr. was sentenced to 40 months in prison after being convicted of obstructing a congressional investigation into Mr. Trump’s 2016 campaign, only for Mr. Trump to deliver an 11th-hour commutation.
Michael Flynn, his first national security adviser, twice pleaded guilty to lying to the F.B.I. during the Russia investigation, but the Justice Department, after an extraordinary public campaign by Mr. Trump, abruptly moved to drop its criminal case against him. In the final months of his presidency, Mr. Trump issued a pardon.
