The current idiom of the Trump probe talks about “shoes falling”. Today it wasn’t so much a shoe but one enormous boot… A general’s army boot no less.

It’s hard to understate the significance of the guilty plea of General Michael Flynn. It represents a historic moment, not simply in terms of the news agenda for the day, week, or month. This is a pivotal moment that might well be measured in historic terms for the American Republic.

Let’s be clear: Michael Flynn served at the side of Trump throughout the campaign and, it might be argued, was closer to the candidate than almost anybody. Trump trusted him and that trust translated into loyalty both ways. Even after he’d been fired from the White House, Trump is said to have considered rehiring him. He was Trump’s man far more than even Vice President Mike Pence. There was even a big question if he would ever flip. Today’s events were never a certainty.

Secondly, the significance here isn’t necessarily that Flynn pleaded guilty to lying to the FBI about the campaign’s links to Russia. Lying to the FBI is significant and could (indeed often does) lead to prison time. What’s significant is what Flynn hasn’t admitted. There’s still the question of his working as a foreign agent, breaking the Foreign Agents Registration Act (FARA). He’s also not pleaded guilty to his involvement to extradite (dare one say, even, kidnap) Fethullah Gülen to Turkey. Given the evidence that has been mounting, Special Prosecutor Robert Mueller could have charged Flynn with so much more.

Given that Mueller had a reputation as a strict prosecutor, the extent of the charges it looks like he’s willing to overlook would indicate that Flynn has made a big offer. Certainly, Flynn’s statement seems to hint at nothing less. It does nothing to hide the fact that he is already trying to spin a narrative in which he is portrayed in heroic terms.

“My guilty plea and agreement to cooperate with the Special Counsel’s Office reflect a decision I made in the best interests of my family and of our country. I accept full responsibility for my actions.”

He speaks of “family” but the big word there is “country”. Flynn has a way out of his current legal and financial predicament. Rumours that he’s willing to say that Trump directed him to contact the Russians go right to the heart of the story. It undercuts everything that Trump has claimed for the past eighteen months.

One other point worth bearing in mind: in admitting his guilt, Flynn has justified former Acting Attorney General Sally Yates’ actions when she told the White House that the new National Security Adviser had been compromised by the Russians. It also justifies James Comey’s investigation. It also makes Donald Trump’s attempts to block the investigation look like a solid case of obstruction of justice.

Now, of course, we should temper today’s news with some hard politics. Just because Flynn admitted to one charge and might provide testimony in the future does not mean we’re close to the impeachment of the President. Republicans are remaining defiant for a variety of reasons, not least that they feel like they have been backed into a position from which it’s almost impossible to escape. Today it looks like they’ll pass their Tax Bill. That would be a small victory for Mitch McConnell and the traditional wing of the party (small because the plan is far from popular or something they might wish to boast about too much) but would, nevertheless, represent a victory they can take forward.

So, what happens next?

In terms of the investigation, one can assume that Flynn will not be the end of the story. Trump’s lawyer, Ty Cobb, has previously assured the President that the investigation would be over by Christmas. This is now certainly not going to happen (and, in truth, it was never going to happen anyway with Paul Manafort’s trial set for spring next year). Mueller’s team has been speaking with Jared Kushner and, really, that would probably be the next ‘shoe’ we should expect to drop. If that happens, then really all bets are off as to where this goes. It’s said that Kushner would not wish to go the way of his father who served fourteen months of a two year prison sentence for witness tampering. What that means is really anybody’s guess.

The more interesting question is really how the Republicans respond. There has always been an obvious ‘escape route’ but that required them to distance themselves from a President who has never really represented them. They could, in metaphorical terms, come running from the Capital Building claiming to have been held hostage for all these months. That made more sense after the mid-terms, which is why the two prominent anti-Trump Republicans, Jeff Flake and Bob Corker, are not running for re-election. That logic would still hold but some might begin to feel that time is running out. The closer that Mueller gets to the Oval Office, the less likely that Republicans will want to stick with the President.