Michael Flynn, former national security adviser to former President Donald Trump, speaks to attendees as he endorses New York City mayoral candidate Fernando Mateo during a campaign event on June 3, 2021, in Staten Island, N.Y. Eduardo Munoz Alvarez/AP hide caption
Michael Flynn, President Trump's former national security adviser, leaves federal court with lawyer Sidney Powell in September 2019. Manuel Balce Ceneta/AP hide caption
Michael Flynn, here at Trump Tower in December 2016, spent less than a month in the role of President Trump's national security adviser. John Angelillo/Pool/Bloomberg via Getty Images hide caption
Former national security adviser Michael Flynn leaves the federal courthouse in Washington in June. Flynn's attorneys say newly released documents prove the FBI laid a "perjury trap" for their client. Manuel Balce Ceneta/AP hide caption
Michael Flynn, President Trump's former national security adviser, leaves federal court following a status conference with U.S. District Judge Emmet Sullivan in Washington in September. Manuel Balce Ceneta/AP hide caption
This courtroom sketch depicts former national security adviser Michael Flynn, standing center, flanked by his lawyers, listening to U.S. District Judge Emmet Sullivan on Tuesday in Washington, D.C. Dana Verkouteren via/AP hide caption
Former Trump national security adviser Michael Flynn leaves federal courthouse in Washington in July, following a status hearing. Manuel Balce Ceneta/AP hide caption
President Trump's national security adviser Michael Flynn leaves federal courthouse in Washington on July 10. Flynn has pleaded guilty to lying to the FBI and is scheduled to be sentenced later this month. Manuel Balce Ceneta/AP hide caption
Donald Trump waits to step onto the portico for his presidential inauguration on Jan. 20. Patrick Semansky/AP hide caption
White House senior adviser Jared Kushner listens as President Donald Trump speaks during a Nov. 1 cabinet meeting at the White House. Evan Vucci/AP hide caption
President Trump meets with congressional leaders in the Oval Office at the White House on Sept. 6. The deadline to fund the government and raise the debt ceiling is coming up on Dec. 8. Alex Wong/Getty Images hide caption
President Trump speaks on the phone in January with Russian President Vladimir Putin, joined by top White House figures Reince Priebus (from left), Vice President Pence, Steve Bannon, Sean Spicer and Michael Flynn. Only Pence remains. Drew Angerer/Getty Images hide caption
Former FBI Director James Comey takes his seat to testify at a Senate Intelligence Committee hearing on Capitol Hill on Thursday. Andrew Harnik/AP hide caption
Then-national security adviser Michael Flynn speaks at the White House earlier this year. He has agreed to turn over business documents to senators investigating Russia's meddling with the 2016 elections. Carolyn Kaster/AP hide caption
Former national security adviser Michael Flynn sitting in the White House in February. The Senate Intelligence Committee announced it has subpoenaed two companies owned by Flynn. Carolyn Kaster/AP hide caption
Michael Flynn (with his hand to his ear) sits next to Russian President Vladimir Putin at a dinner in Moscow on Dec. 10, 2015, celebrating the 10th anniversary of RT, an English-language TV channel funded by the Russian government. Mikhail Klimentyev/AP hide caption
President Trump waves as he arrives to give the commencement address at the U.S. Coast Guard Academy on Wednesday. Susan Walsh/AP hide caption
National Security Adviser H.R. McMaster, right, takes to the stage Tuesday at the White House after being introduced by Press Secretary Sean Spicer. Both of them, as well as Vice President Mike Pence, have had their credibility damaged after issuing denials that President Trump later reversed. Susan Walsh/AP hide caption
President Trump weighed back in on Twitter, apparently trying to switch subjects, from the troubles of his former national security adviser to raising the possibility of a government shutdown. NurPhoto/NurPhoto via Getty Images hide caption
Michael Flynn, seen here arriving for a news conference in the East Room of the White House in February, is being investigated by the inspector general of the Department of Defense, Rep. Elijah Cummings said Thursday. Evan Vucci/AP hide caption
House Oversight Committee Chairman Jason Chaffetz, R-Utah (right), and ranking member Rep. Elijah Cummings, D-Md., speak to reporters about Michael Flynn, President Trump's former national security adviser, on Tuesday in Washington, D.C. Win McNamee/Getty Images hide caption
Then-Deputy Attorney General Sally Yates speaks during a news conference at the Department of Justice in Washington, D.C., in 2016. Yates is scheduled to appear before the Senate Judiciary Committee on May 8. Pete Marovich/Getty Images hide caption
Former national security adviser Michael Flynn's lawyer says Flynn has offered to testify about Trump campaign contacts with Russia if he gets immunity from prosecution. Flynn is seen at the White House on Feb. 13. Evan Vucci/AP hide caption
Top House Democrats, including Rep. Elijah Cummings, D-Md. (at the podium), said this week they want an investigation into President Trump's connections with Russia, such as when he learned that his national security adviser, Michael Flynn, had discussed U.S. sanctions with a Russian diplomat. J. Scott Applewhite/AP hide caption