It's been 420 days in the making, but President Trump scored bigly on Friday when Senate Republicans officially confirmed his nominee, Judge Neil M. Gorsuch, for the vacant ninth seat on the Supreme Court.

He should savor this moment, because this may be the last time in a while that he can celebrate a major success.

Yes, Republicans control both chambers of Congress and the White House and have successfully maintained the conservative balance of power in the Supreme Court. But they accomplished that last thing only after blowing up a centuries-old rule that allows (but not requires) senators to demand a Supreme Court nominee get 60 votes (instead of a majority 51) to get confirmed.

Unless Republicans want to blow up Senate rules even further (for now, they don't), it's very likely that for the next two-ish years of this Congress, Trump's proposals will be dead on arrival in a severely partisan Senate.

To understand why, we have to dig a little into Senate procedure, so bear with me: After pulling the trigger that killed what was left of senators' ability to filibuster nominees on Thursday, Senate Majority Leader Mitch McConnell (R-Ky.) promised he wouldn't kill it dead any further. That means any senator can still filibuster legislation by raising an objection to it, which requires three-fifths of the Senate (60 votes) to get past that objection.

And that means Senate Democrats still have one very critical weapon in the all-out war they've launched against Trump. Senate Republicans don't control three-fifths of the Senate. They have 52 members, and they haven't been able to reliably count on the 10 Trump-state Democrats up for reelection in 2018 to cross party lines on high-profile partisan battles.

And that means the 48 senators who caucus with the Democrats will have the power to hold up most major pieces of legislation Republicans try to undertake. We're talking tax reform, health-care reform, infrastructure reform, defunding Planned Parenthood; you name it, Democrats could conceivably block it. (There are imperfect ways around the filibuster, which I explain here and here.)

It's also possible that getting Gorsuch on the bench could backfire on Trump. Republicans just overrode a rare Democratic filibuster of a Supreme Court nominee; Democrats may in turn be even more motivated to block anything else Republicans want to do.

Talking to reporters Friday minutes before officially confirming Gorsuch (with all but three Senate Democrats voting against his confirmation), McConnell acknowledged the irony of all this.

“I would be the beneficiary — and my party would be the beneficiary — of changing that,” he said of undoing the legislative filibuster. “I'm opposed to changing that. I think that's what fundamentally changes the Senate.”

Here, almost everyone in the Senate agrees with him. The filibuster is the chamber's most defining feature, a feature that requires senators to actually win critics over to get controversial stuff done. It's what makes the chamber so different from the House of Representatives, where what the majority wants, the majority gets.

Actually, wait. I'll amend that statement above to: On keeping the legislative filibuster, almost everyone in the Senate agrees with McConnell. For now.

As the Gorsuch battle underscored, both Republicans and Democrats in Washington are feeling an immense pressure from their bases to stick it to the other side at all costs. The magnetic pull to the poles has created a sense of political nihilism in Washington, The Fix's Aaron Blake writes, an environment that forces even the Senate's old guards of institution to throw up their hands and say: “What the hell. Blow it up.” (No one actually said that, but hopefully you get my point.)

In this context, it's not hard to see how the legislative filibuster soon slips away, too, says The Post's James Hohmann. The president certainly has little regard for political norms; he had no problem urging Republicans to blow up the filibuster for nominees long before they had accepted the idea.

And if Trump's agenda gets stuck in the mud thanks to Senate Democratic filibusters, well ... we'll have a chance to see what he says.

Because that's exactly what's about to happen.