More and more, this year’s unpredictable presidential race is starting to resemble one of Louisiana’s notoriously eventful governor contests. But which one?

The go-for-broke infighting that’s come to dominate the Republican primary can’t help but evoke the end stages of last year’s Louisiana primary, when Public Service Commissioner Scott Angelle and then-Lt. Gov. Jay Dardenne unloaded on GOP frontrunner U.S. Sen. David Vitter.

Their attacks lived well into the runoff election, thanks to a powerful ad that replayed choice debate lines. “We have a stench that is getting ready to come over Louisiana if we elect David Vitter as governor,” Angelle said, on what felt like an endless televised loop. “He’s ineffective. He’s vicious. He’s lying,” chimed in Dardenne.

Republicans who hope to stop Donald Trump, take note. It would be easy to stitch together an equally brutal ad using clips from his GOP rivals, not to mention a blistering speech from 2012 nominee Mitt Romney.

“There is no way we’re going to allow the party of Reagan or the conservative movement to be taken over by a con man,” Florida U.S. Sen. Marco Rubio might say. “I think in terms of a commander-in-chief, we ought to have someone who isn’t springing out of bed to tweet in a frantic response to the latest polls,” Texas U.S. Sen. Ted Cruz could weigh in. And from Romney, ad-makers would have a choice of withering criticisms; in a single speech Thursday, Romney called Trump a “phony,” said he embraced “ridiculous and outrageous” foreign policy positions and noted his penchant for belittling just about every group out there, from Muslims to women to the disabled.

As vicious as such an ad could be, though, it probably would pack much less of a punch.

Blame the general public mood. Many people who watched the gubernatorial ad sympathized with Angelle and Dardenne after watching Vitter savage them, often misleadingly. Trump too is playing the bully, but you don’t see many tears for his opponents or for the GOP establishment that hopes to stop him.

And blame that establishment itself for undermining its own message. Trey Ourso, the consultant who produced the anti-Vitter ad for a Democratic super PAC, has said one of its goals was to make it impossible for either Dardenne or Angelle to turn around and endorse Vitter against John Bel Edwards (and indeed, neither did).

But, when cornered at the end of Thursday’s contentious debate, both Cruz and Rubio admitted that, despite everything they’d just said, they’d back Trump if he were the party’s nominee. As for Romney, he could have rejected an endorsement four years ago, when Trump was already well into his offensive birther campaign against President Barack Obama. Instead, he made a big show of accepting it.

So while there may be similarities to Louisiana 2015, the presidential race is really shaping up more as a repeat of the 1991 runoff between Republican former Ku Klux Klan leader David Duke — who just so happens to be in Trump’s corner — and, by then, widely discredited Democratic ex-Gov. Edwin Edwards. That’ll be particularly true if Trump wins the nomination and faces the front-runner on the Democratic side, former Secretary of State Hillary Clinton.

Back then, the Republican adults in the room took part in an all-out civic effort to avert disaster.

The anti-Duke coalition zeroed in on his personal qualities, publicizing evidence that he had not abandoned his racist ways and that he was a tax cheat. It called on voters who had well-founded doubts about Edwards to put them aside for the greater good; that’s the message behind the infamous “Vote for the Crook. It’s Important” bumper sticker. It predicted economic calamity if Duke won, with businesses fleeing the state.

There’s much here for anti-Trump forces to emulate. Trump too has a long track record of offensive statements and a trail of financial questions. Clinton also has baggage that skeptical voters would need to set aside, at least in the eyes of many Republican voters. And level heads are predicting an equally devastating loss of stature should Trump win, in this case not in the business world but on the world stage.

The fact that Louisiana once flirted with someone so unfit for the top job doesn’t exactly inspire civic pride, and nor should it. But give the state this: When it comes to pulling back from the brink, nobody has more to teach the rest of the country.

Stephanie Grace can be contacted at sgrace@theadvocate.com. Follow her on Twitter, @stephgracenola.