Now, months after Donald Trump announced his candidacy with a potentate’s flair, weeks after he diminished and belittled one after another of the touted GOP presidential lineup, and days after he swept Super Tuesday and led the delegate race, the Republican establishment is hitting the panic button.

It’s about time.

Trump is almost without doubt the most outrageous, outsized candidate ever to appear on the American political landscape. He says out loud what some only whisper in private. He’s not the first candidate to bash immigrants, support waterboarding and criticize past presidents, but others have done so more subtly. Trump rips off the cloaking language, doubles down, then dares others to challenge him.

After predicting Trump would burn out on his own, those in the party establishment are frantically searching for ways to stop him. They drafted Mitt Romney to denounce Trump as a phony who lacked the temperament, moral character or judgment to be president. That attack was diminished somewhat by Romney’s eager pursuit of Trump’s endorsement in 2012, during which he lavished praise on the New York businessman’s success, job-creating ability and stand against China on trade. It also should be noted that Romney’s courting of Trump came despite Trump’s scurrilous “birther” campaign against Obama and after the New York state attorney general announced an investigation of Trump University — which already had been forced to change its name because, well, it wasn’t a real university, just real estate seminars in hotels.

The choice of Romney as the party’s vanguard against its front-­runner is ironic in another respect: It was Romney’s defeat in 2012 that prompted Trump to plan a White House run.

Now, as the front-runner careens toward the nomination like a cyclone, the party’s problem is twofold. Lining up its heaviest hitters against him may give greater credence to the perceived threat that Trump poses to the existing political order. A rally in Michigan on Friday morning was packed with raucous, frenzied supporters who showed no signs of diminished affection for their hero. The even bigger dilemma is that party leaders have yet to agree on a candidate around whom they can coalesce. Many, like John McCain, are sending a mixed message by denouncing Trump, then meekly admitting they will back “whoever is the nominee.”

To stop Trump — and it’s no longer clear that is possible — Republicans must find the courage to put their resources behind a viable alternative. And they should move quickly. On Tuesday, another four states will hold their contests, and polls showed Trump leading in two of those, the delegate-rich troves of Michigan and Mississippi.

Picking a lane, in the parlance of this election, will put off some Republicans, particularly those who believe the party’s cardinal sin in 2008 and 2012 was its failure to back “a true conservative.” But Texas Sen. Ted Cruz has failed to demonstrate that he can win a majority even of the evangelicals that form his base, let alone the mix of Republicans and independents needed for November. There also are those — the Star Tribune Editorial Board among them — who consider his ultra-combative, shut-’er-down temperament a poor fit for the presidency.

That leaves Sen. Marco Rubio of Florida and Ohio Gov. John Kasich. The Editorial Board already took the rare step of issuing a pre-caucus endorsement, for Rubio. He remains the best suited to take on Trump and advance to November with a platform that would be conservative — he is, in truth, no moderate — but appealing to a broader cross-­section of voters.

Kasich, despite his inability to break out of single digits, continues to impress with an evenhanded approach and old-school restraint that hark back to a time when candidates could disagree without being disagreeable. A Rubio-Kasich ticket would offer a more formidable pairing and would present an option far more attractive than the chaotic brawl that could come from a brokered convention in July.

For now, the GOP should seriously consider throwing itself behind the joint ticket of a candidate who offers a fresh vision and diversity the party badly needs, and one whose experience and demeanor would do credit to Republicans and provide a steady hand.

The last team to offer such a combination of traits won the White House. Twice.