Michael Flynn, President Donald Trump’s mercurial national security adviser, submitted his resignation late Monday amidst growing controversy over his communications with Russia’s ambassador to the United States.

Flynn wrote in his resignation letter that he provided “incomplete information” about conversations with Ambassador Sergey Kislyak.

Critics are questioning whether top Trump administration officials were misled, lied to — or perhaps, complicit. And beyond the disruption caused by the resignation of a senior official so early in a new administration, the circumstances surrounding Flynn’s departure will almost certainly increase scrutiny of others in Trump’s inner circle who allegedly have ties to Russia. 

The conversations between Flynn and Kislyak reportedly began before the Nov. 8 presidential election and continued as outgoing President Barack Obama imposed sanctions against Russia in December — for allegedly meddling in that election. The narrative about what they discussed had become increasingly murky prior to the resignation.

Flynn, a retired three-star Army general, denied last Wednesday that he’d discussed sanctions with Kislyak, according to The Washington Post.  The next day, the Post reported, a spokesman for Flynn “indicated that while he had no recollection of discussing sanctions, he couldn’t be certain that the topic never came up.”

That was more than three weeks after Vice President Mike Pence had defended Flynn on CBS’ “Face the Nation.”

Pence was asked about a report that Flynn had talked with the Russian ambassador on the day that the sanctions against Russia were announced.

“What I can confirm, having spoken to him about it, is that those conversations that happened to occur around the time that the United States took action to expel diplomats had nothing whatsoever to do with those sanctions,” Pence told CBS’ John Dickerson on Jan. 15.

More recently, Trump administration officials have struggled with their message.

White House senior policy adviser Stephen Miller dodged when asked Sunday on NBC’s “Meet The Press” whether Trump had confidence in Flynn.

Miller told host Chuck Todd that was a question “you should ask the president” or White House Chief of Staff Reince Priebus.

Kellyanne Conway, counselor to the president, told MSNBC Monday afternoon that Flynn had “the full confidence of the president.”

Hours later, White House Press Secretary Sean Spicer said Trump was “evaluating the situation.”

‘Incomplete information’

Flynn wrote in his resignation letter that as the incoming national security adviser, “I held numerous phone calls with foreign counterparts, ministers, and ambassadors.”

“Unfortunately, because of the fast pace of events, I inadvertently briefed the vice president-elect and others with incomplete information regarding my phone calls with the Russian ambassador,” Flynn wrote. “I have sincerely apologized to the president and the vice president, and they have accepted my apology.”

The White House released a copy of the letter. Flynn did not describe what he had specifically discussed with Kislyak.

Trump named retired Army Lt. Gen. Joseph K. Kellogg Jr. as the acting national security adviser. Kellogg is a highly decorated Vietnam War veteran.

California Republican Rep. Devin Nunes, chairman of the House Intelligence Committee, praised Flynn in a statement late Monday.

“Michael Flynn served in the U.S. military for more than three decades,” he said. “Washington, D.C., can be a rough town for honorable people, and Flynn — who has always been a soldier, not a politician — deserves America’s gratitude and respect for dedicating so much of his life to strengthening our national security.”

‘He got caught’

Others in Congress were less charitable.

California Democratic Rep. Eric Swalwell suggested in a statement that Flynn is “only resigning because he got caught by the press for improper prior and existing relationships with Russia.”

“Questions remain about whether he made such contact of his own volition or on orders; whether Trump administration officials were misled about the contact or lied to cover it up; and whether Flynn might’ve been susceptible to Russian blackmail, as the Justice Department reportedly informed the White House late last month,” Swalwell wrote.

The Washington Post has reported that acting Attorney General Sally Q. Yates told the White House in late January that she believed Flynn had misled senior administration officials about what was said and warned that he could be vulnerable to blackmail. Yates was fired by Trump late last month for refusing to enforce his executive order on immigration.

Swalwell described Flynn’s contacts with Kislyak as “part of a larger pattern of Russian involvement with and support for Trump and his team before and since the 2016 election.” He and other House Democrats have called for an independent, bipartisan commission “to investigate Russian interference in the 2016 election.”

New York Democrat Eliot L. Engel, the ranking member on the House Foreign Affairs Committee, echoed the call for a bipartisan investigation.

“Far too many questions remain unanswered about this administration’s ties to Russia,” he said in a statement. “The latest reporting shows that Gen. Flynn was in contact with Russian officials during the campaign, and we know Putin was working to tip the scales in President Trump’s favor.”

Where such an investigation might lead appeared to be on the minds of several Democratic members of Congress late Monday.

“The Trump administration has yet to be forthcoming about who was aware of Flynn’s conversations with the ambassador and whether he was acting on the instructions of the president or any other officials, or with their knowledge,” California Rep. Adam Schiff, the ranking Democrat on House Intelligence, said in a statement.

Michigan’s John Conyers Jr., ranking Democrat on the House Judiciary Committee, and Maryland’s Elijah E. Cummings, ranking Democrat on the House Oversight and Government Reform Committee, issued a joint statement on Flynn’s resignation. 

The veteran lawmakers said they were shocked at reports that U.S. law enforcement officials warned the White House counsel that Flynn “had provided false information to the public about his communications with the Russian government, but that the Trump administration apparently did nothing about it.”

“We need to know who else within the White House is a current and ongoing risk to our national security,” Conyers and Cummings wrote, adding that “a full classified briefing by all relevant agencies, including the Department of Justice and the FBI” is warranted.

An early supporter

Flynn was an early Trump supporter who shared his expertise in intelligence and foreign affairs with the campaign.

He was outspoken and provocative. In one tweet, he dared Arab and “Persian” leaders to “step up to the plate and declare their Islamic ideology sick.” He advocated closer ties with Russia, and at the Republican National Convention in Cleveland last July, he also called for Democratic nominee Hillary Clinton to be locked up. 

Flynn had served as director of the Defense Intelligence Agency until he was reportedly forced out in late 2014.

Early on, some critics raised concerns about Flynn’s purported links to Russia. Those included a series of paid speaking engagements he did for RT, the Russian state-run television channel. In 2015, he attended a banquet celebrating the network and was seated next to Russian President Vladimir Putin. 

Several others who are or who been close to Trump also have connections to Russia. 

Among them: Paul Manafort, Trump’s onetime campaign manager, who resigned last August amid questions about his alleged ties to pro-Russia forces in Ukraine; Secretary of State Rex Tillerson, Exxon Mobil’s former CEO, who was awarded the Order of Friendship by Putin in 2013, one of Russia’s highest honors to foreign citizens; and Wilbur Ross, Trump’s Commerce secretary nominee, who reportedly was a business partner with a Russian oligarch.