After a day in which it became increasingly apparent something was brewing at the White House, both CNN and Fox both report that national security adviser Michael Flynn has resigned. The first departure from the Trump administration comes less than four weeks into Donald Trump’s presidency:

Embattled White House national security adviser Michael Flynn resigned Monday night, two sources tell CNN.

His departure came just after reports surfaced the Justice Department warned the Trump administration last month that Flynn misled administration officials regarding his communications with the Russian ambassador to the United States and was potentially vulnerable to blackmail by the Russians.

The move comes less than a month into the job, making him one of the shortest-serving senior presidential advisers in modern history.

Fox confirmed it moments later:

BREAKING: National Security Adviser Michael Flynn has resigned, Fox News confirms

— Fox News (@FoxNews) February 14, 2017

In any other administration, the avalanche of leaks and the near-lack of any defense for an embattled White House player would have made a resignation inevitable. That didn’t seem to be the case at first with Trump, who has a reputation for digging in under fire. The problem this time appears to be twofold: the revelation that the Justice Department had tried to warn the White House about Flynn, and the apparent ire of Vice President Mike Pence for having been misled. Pence is an independently elected official, and more importantly a traditionalist in governance. Flynn made Pence a fool, and Pence was not about to take that lying down.

So now what? Earlier this evening, news began to swirl about a potential replacement coming for a visit:

President Trump and his top advisers will talk with retired Gen. David Petraeus this week as a possible replacement for National Security Advisor Michael Flynn, according to a report.

Trump regularly referenced Petraeus during his campaign speeches last year, telling guests at rallies that the former general was punished more severely for leaking classified information to his mistress than former State Sec. Hillary Clinton was reprimanded for setting up a private email server.

Trump had briefly considered Petraeus for secretary of state. He passed over him due to the earlier incident and the problems that might create with confirmation in the Senate, a hurdle which is not in the way for national security advisor.

That still might present some problems for Trump, who made Hillary Clinton’s serial mishandling of classified material into a powerful attack on her fitness for office. Trump could issue a pardon for Petraeus to clear the official legal record, but that doesn’t really settle the issue as a political concern. And if the issue with Flynn was potential blackmail, what does that say about Petraeus, whose prosecution started because he had an illicit affair with his biographer?

Of course, Petraeus could just be coming in as a consultant. The White House is casting a wider net for Flynn’s replacement, Politico reports:

Earlier it was reported that President Donald Trump’s adviser and son-in-law, Jared Kushner, was involved in a search for candidates to replace Flynn, according to sources close to the administration.

The list of possible replacements includes retired Gen. David Petraeus, who’s scheduled to meet with Trump at the White House on Tuesday, according to two people familiar with the plans. Other possibilities: Stephen Hadley, who served as national security adviser under President George W. Bush; Tom Bossert, who also served as a national security aide under Bush and now oversees cybersecurity under Trump; Adm. James Stavridis, dean of the Fletcher School at Tufts; and Department of Homeland Security head John Kelly.

Kelly should stay put at DHS, but the other potential candidates hold a lot of promise. Hadley and Bossert might be too “neocon” for Trump, but Stavridis has enough credibility to have been on Hillary’s list of potential running mates and Trump’s list of potential Secretaries of State. Any of these would suffice, though, especially on short notice, and would go a long way toward dialing down the controversy surrounding the administration over Flynn now. At least the White House can now start putting this behind them.

Update: Zeke Miller has a picture of the resignation letter:

Breaking: text of Flynn's resignation letter pic.twitter.com/KGue1cJFzL

— Zeke Miller (@ZekeJMiller) February 14, 2017

Trump’s made a temporary appointment in the meantime:

President Trump has named Lt. General Joseph Keith Kellogg, Jr. acting national security adviser following the resignation of Michael Flynn. pic.twitter.com/R2XuBwGwUU

— NBC News (@NBCNews) February 14, 2017

Kellogg had just been appointed chief of staff and executive secretary to the National Security Council, so this maintains continuity until Trump can pick another nat-sec adviser. Kellogg himself might end up on the short list.