Two possibilities arise from the guilty plea of former Trump National Security Adviser Michael Flynn.

Flynn’s plea marks the beginning of the end of the Trump administration. Flynn’s plea marks the end of the desperate hope that America will be delivered from the Trump presidency by impeachment and removal from office on the grounds that his campaign colluded with Russia to win him the 2016 election.

There are other ancillary events one can easily imagine. For example, Trump could fire independent counsel Robert Mueller and/or pardon Flynn and others. But those moves would eventually make the end of his administration far more likely, and so should be considered as part of Possibility #1.

He’s done for — or the impeachment dream is dead. That’s it.

If there was conspiratorial cooperation between the Trump campaign and the Kremlin, Flynn was at the center of it. That much is clear. And Mueller has Flynn on the hook. Analysts speculate that Flynn was allowed to plead down to a relatively minor charge in exchange for a promise of full cooperation. Should Mueller believe Flynn is failing to cooperate, he could make Flynn’s future unendurable (in part by going after Flynn’s son).

It’s therefore fair to assume Flynn will come clean about what he knows.

And that’s why this will lead either to Trump going down in flames or the impeachment-now movement getting its heart ­broken.

For my friends in the impeachment camp, I’d recommend preparing for heartbreak (and not just because you should never expect things to go the way you want; trust me, I wanted Rubio).

The Flynn plea comes after Mueller’s moves on three other Trump officials — indictments of onetime campaign manager Paul Manafort and his deputy Rick Gates, and a plea arrangement with lower-level campaign guy George Papadopoulos.

But as the former federal prosecutor Andrew C. McCarthy notes, none of the indictments or pleas in any of these cases goes right at the central impeachable offense here, which would be a conspiracy to affect the results of the 2016 election.

Manafort and Gates are accused of having played fast and loose with money and federal regulations — but their offenses actually precede their roles on the Trump campaign. Flynn pleaded guilty to lying to FBI agents about the substance of phone calls between him and the Russian ambassador — calls made weeks after the election.

That means Mueller doesn’t have the goods. Yet. If Mueller had evidence that This Specific Thing and That Specific Thing and the Other Specific Thing took place between the Trump campaign and Russian contacts in the summer and fall of 2016, those Things would be part and parcel of the indictments and pleas he would have reached already.

Instead, it appears he’s adopted a strategy of getting these guys with whatever he can get them for so that they might provide him with the details and the narrative he needs. In other words, the Flynn plea is part of a fishing expedition.

If there are fish, Trump likely won’t survive. That’s pretty inarguable now. No one is getting out of this one without answering Mueller’s questions — maybe not even Trump.

But they’ll need to answer in part because Mueller will still be fishing. And the fish he needs to catch can’t simply be fish from Russia that happen to be floating nearby. The issue isn’t that Flynn had contact with the Russians. The issue won’t even be that Flynn had contact with the Russians on orders from bumbling Trump son-in-law Jared Kushner, which ABC News reported Flynn was ready to tell Mueller.

Campaigns have made contact with foreign powers for decades. Democratic presidential nominee George McGovern sent an emissary to meet with the North Vietnamese while Americans were dying every day in a war against them, for God’s sake.

Absent real evidence of a conspiracy, Trump will not be driven from office for any of this. We’ll know soon enough whether the expedition hooks a giant marlin or whether it’s been much ado about goldfish.