HACKBERRY, La.—President Donald Trump came to southern Louisiana on May 14 to extol the benefits of U.S. energy production but could not resist a slashing critique of the Democrats battling to face him in the 2020 presidential race.

"I'm looking at the competition. You sort of dream about competition like that, you know?" he told several hundred workers at the Cameron LNG export terminal in Hackberry, La.

Trump's review of the candidacies of South Bend, Ind., Mayor Pete Buttigieg, former Vice President Joe Biden, former congressman Beto O'Rourke and U.S. Senators Elizabeth Warren and Bernie Sanders showed he was keeping a keen eye on the crowded Democratic presidential contest.

After talking up the benefits of LNG exports, Trump dove into his assessment of Democratic presidential contenders, who are eager to deny him a second term and have bashed his presidency on the campaign trail.

He drew out the pronunciation of Buttigieg's surname, which the candidate pronounces as "Boot-edge-edge," and noted O'Rourke's bid to relaunch his campaign after his initial outing fizzled with voters.

"Beto is falling fast. What the hell happened? Remember, about four weeks ago, he said: 'I was made for this.' He was made for it. He was made to fall like a rock," said Trump.

Then he turned to Biden, the front-runner in the Democratic field that now numbers more than 20.

"I don't know what the hell happened to Biden. What happened to him? I'm looking and I said: 'That doesn’t look like the guy I knew.' What happened to him?" asked Trump.

Trump, who has in the past dubbed Sanders "Crazy Bernie," returned to that theme on Tuesday, saying: "You know, Bernie is crazy." But he added: "Bernie has got a lot more energy than Biden, so you never know."

Trump, with an approval rating in the low 40 percent range, is no shoe-in for re-election. He has a strong economy on which to campaign, but his divisive policies on issues such as immigration as well as his trade war with China and struggles with Iran, North Korea and Venezuela could prove serious obstacles.

But he expressed confidence in his chances.

"Boy, you got some beauties there. Three hundred and fifty million people and that's the best we can do. I don't think so. Even as Democrats, I could pick better than that," he said.

Trump later traveled to the New Orleans suburb of Metairie, for a campaign fundraiser. The event, attended by 225 people, raised $4 million for his campaign and the Republican National Committee.