President Donald Trump used insults to welcome New York Mayor Bill de Blasio into the 2020 presidential race, a strategy he has reserved for only a few Democratic candidates.

Trump wasted little time in slamming candidates like now-front-runner and former Vice President Joe Biden, former Texas Democratic Rep. Beto O’Rourke, Massachusetts Sen. Elizabeth Warren and Sen. Bernie Sanders of Vermont, the 2016 Democratic runner-up. He has said very little about South Bend, Indiana, Mayor Pete Buttigieg and California Sen. Kamala Harris, even though she drew a large crowd at her Oakland campaign kickoff event — noteworthy because the president often remarks on his rally crowds and those drawn by his rivals, which he typically claims are much smaller.

“The Dems are getting another beauty to join their group,” Trump tweeted Thursday morning, two days after he told an audience in Louisiana that the field of more than 20 Democrats include “some beauties.” He told reporters Monday “l like what I see” in a field he believes will produce a nominee he can defeat in the general election.

Trump claimed de Blasio, who has ties to the Clintons, is “considered the worst mayor in the U.S.”

But he wasn’t finished slamming the Big Apple’s chief executive, who has been sharply critical of his fellow New Yorker who now resides in the White House.

“He is a JOKE, but if you like high taxes & crime, he’s your man. NYC HATES HIM!” Trump wrote in a tweet. Here, the president has a point, even if his rhetoric is typically rigid: A recent Quinnipiac poll found de Blasio’s approval rating in New York City is below 40 percent.

The Dems are getting another beauty to join their group. Bill de Blasio of NYC, considered the worst mayor in the U.S., will supposedly be making an announcement for president today. He is a JOKE, but if you like high taxes & crime, he’s your man. NYC HATES HIM!

— Donald J. Trump (@realDonaldTrump) May 16, 2019

But Trump’s decision to engage the New York mayor’s planned entry is notable. That’s because he has saved his Twitter attacks for candidates he has admitted to seeing as his likely general election foes, or appears to fear could catch fire and pose a serious risk.

The latter list includes O’Rourke and Buttigieg — and possibly de Blasio, even though the same poll found de Blasio’s unfavorable rating nationally is higher than his favorability score.

On April 29, hours before Biden’s first rally, Trump went to Twitter to paint the former VP as lacking the energy necessary to run a campaign — much less become the so-called “leader of the free world.”

“Sleepy Joe Biden is having his first rally in the Great State of Pennsylvania. He obviously doesn’t know that Pennsylvania is having one of the best economic years in its history, with lowest unemployment EVER, a now thriving Steel Industry (that was dead) & great future!” Trump wrote.

Sleepy Joe Biden is having his first rally in the Great State of Pennsylvania. He obviously doesn’t know that Pennsylvania is having one of the best economic years in its history, with lowest unemployment EVER, a now thriving Steel Industry (that was dead) & great future!……..

— Donald J. Trump (@realDonaldTrump) April 29, 2019

In February, when Sanders officially jumped in, Trump signaled he would welcome the self-proclaimed democratic socialist winning the nomination — and used another nickname to try and paint him as unhinged: “Crazy Bernie has just entered the race. I wish him well!”

Crazy Bernie has just entered the race. I wish him well!

— Donald J. Trump (@realDonaldTrump) February 20, 2019

After O’Rourke entered the race, Trump reserved his attacks for when he was in front of the cameras in the Oval Office, mocking the former congressman’s habit of gesturing with his hands when he speaks.

“I’ve never seen so much hand movement,” Trump said in a mocking tone while wearing a smirk. “I said, ‘Is he crazy or is that just the way he acts?’”