Peter Navarro, a former trade adviser to Donald Trump, began a four-month jail term for contempt of congress in federal prison on Tuesday.
Navarro, 74, was convicted last year after ignoring a subpoena from a House committee investigating the Capitol riot on 6 January 2021.
A Supreme Court justice denied his last-ditch appeal to stay out of prison on Monday.
He will be the first Trump-era official to be jailed for contempt of Congress.
Navarro stopped in the parking lot of a shopping centre to speak to reporters before reporting to federal prison in Miami. The facility, FCI Miami, is a low security facility with an adjacent minimum security camp.
Wearing the bomber jacket that he was seen in while addressing the annual conservative meeting known as CPAC, Navarro repeated his defence in the case to a handful of reporters.
Along with advising on trade, Navarro worked on strategies to try to overturn the 2020 election and keep Mr Trump in the White House. People who stormed Capitol Hill on 6 January 2021 sought to stop lawmakers from certifying that Mr Trump lost the election.
Navarro was first served with a subpoena by the US House of Representatives select committee in February 2022, but did not hand over any of the emails or documents requested.
When contacted by the committee, Navarro said that former President Trump had instructed him to cite executive privilege, a legal principle allowing some White House communications to be kept private.
The judge in the case ruled Mr Trump could not make that request or executive privilege did not shield Navarro from the subpoena.
At the end of January, three years after the attack on congress, Navarro was given the sentence and fined $9,500 (£7,500).
Navarro had sought to remain free while appealing his conviction, with his attorneys arguing that he was "indisputably" not a flight risk or threat to the public.
Earlier this week, Supreme Court Chief Justice John Roberts Jr refused to delay the sentence.
In a 2021 memoir - entitled In Trump Time - Navarro said he was the architect of a strategy to challenge the 2020 election's results that made Joe Biden president.
The plan called for congressional Republicans to delay certification of Mr Biden's electoral victory, a standard procedure that was scheduled for 6 January 2021. The House committee noted that Navarro's claims of electoral fraud had been repeatedly determined to be baseless by state and local officials.
Another Trump-era official, former campaign strategist Steve Bannon, was also convicted of two counts of contempt for refusing the committee's summons and sentenced to four months in jail.
Bannon, however, has been allowed to stay out of prison while his defence team appeals.
