If you think Obama was just lucky on Syria, you’re wrong. But something else happened this week that set the president’s good luck vaults to overflowing: support in the Senate for Larry Summers cratered before Obama could nominate him as Fed chair. This development spared Obama immeasurable misery in his remaining three-plus years. I hope he knows this, and I hope he takes the right lesson from it, which is that to deal with a GOP that shows signs only of (believe it or not) increasing hysteria, he needs his base behind him the rest of the way, and he ought to behave accordingly.

Conjure with me, if you will, this mental image. In this alternative universe, Montana Democrat Jon Tester, whose announced opposition to Summers was the stake in the heart, played his cards closer to his vest for whatever reason. And sometime next week, say, Obama stood at that presidential podium with Summers at his side, extolling the luminous brilliance of the man, as Obama would have put it, who was exactly the right person for the Fed job.

What would have happened? A palace revolt among liberals across the country, that’s what. I try to keep my ear fairly close to the earth on these matters. And based on the admittedly anecdotal scuttlebutt I was hearing, I think that if Obama had gone ahead with Summers it would have been by far the most damaging single event in his relationship with liberals in his entire tenure. Worse than no public option in the health bill. Worse than Rahm Emanuel saying liberals were “fucking retarded.” Worse than threatening to bomb Syria (and it wouldn’t have helped to have been coming right on the heels of that one, either). Worse even than what I consider his nadir thus far, the 2011 debt-ceiling fiasco.

Why? Because liberals’ minds are made up about Summers. Under Bill Clinton, he was for consolidation and deregulation. It’s written in stone in people’s minds. Less well known is the fact that in 2009, Summers was taking pretty progressive positions, arguing for a stimulus greater than $1 trillion. But his free-market rep predates that. Plus, there’s his reputation as a sexist jerk, which does appear to have been rather well earned.

Piquancy is added to the last point because the other main contender for Fed chair is a woman, and a highly qualified one at that. In fact Janet Yellen is more highly qualified for this particular job than Summers. There has never been a female Fed chair, so for Obama to have passed her over for a man who once said that women weren’t quite up to snuff to compete in the sciences would have been enraging to liberals. Obama gave the impression not only of not caring about this, he gave the impression of not even knowing that Yellen was a woman when he slipped up at a summer press conference and called her “Mr. Yellen.”

Obama has never been fond of his liberal base or gone out of his way to please it.

If he’d gone against Yellen in favor of Summers, his backing among rank-and-file liberals would have nosedived. His support among liberal Democrats on Capitol Hill would have taken an extremely serious hit, too, at precisely the time when the huge showdowns are coming over the budget and the debt limit. The White House might have been able to force a favorable Summers vote through the Senate by calling in every chit it had out there, but it would have left a horrible taste in many legislators’ mouths, and the tension between the White House and Hill Democrats would have been enormous.

Obama developed this blind spot about Summers that I’ve heard tell about. Apparently Summers is, or can be, utterly dazzling in person, polymathically impressive across a range of topics. Men like his company. Or something. Obama was not immune. But Tester did POTUS a huge favor by announcing his opposition when he did, forcing Summers and the White House to realize the votes just weren’t going to be there.

I do hope Obama understands this. And if he does understand it, I hope against hope that it doesn’t lead him to exactly the wrong conclusions. What I suspect is that this will make Obama angry at the liberal base. He’s never been very fond of it, never really gone out of his way—from dropping the public option to offering entitlement cuts to John Boehner to various appointments, most especially in the economic and financial sector—to please the base. There seems every chance that he decides to conclude from this that those pesky liberals prevented him from further communion with his man Larry.

He needs to conclude just the opposite. This fall, the Republicans are going to be crazier than ever and dig in harder than ever. I know that seems impossible. But it’s just going to get worse. This push to defund Obamacare won’t succeed, but it’s the most grandiose kamikaze mission they’ve engaged in yet, and there’s no telling what furies it will unleash. When it does, Obama is going to need Democratic legislators and liberals across the country firmly and loyally in his corner.

GOP obstinacy is costing him points and support. His approval rating has wavered lately partly from self-inflicted wounds—the NSA-surveillance revelations, the Syria situation. But I think mostly it’s people in the middle starting to give up on the possibility that Obama, with this Congress, can get anything done at all. And maybe he can’t. But there’s only one way he can. Put it all on the line next fall, campaign as if he were on the ballot, make sure Democratic constituencies turn out to vote, throw everything into taking back the House, and take the fight to the other side. That’s how he needs to spend the next three years. He should call Tester and thank him. Then he should just name Yellen (if he names someone else after all this, it won’t be quite like naming Summers but it won’t go down well). And then he should decide that, in addition to leading the country, he’s leading a movement.