Republican presidential front-runner Donald TrumpDonald TrumpLiberals don't understand difference between news and opinion Rubio: Former campaign aides targeted by IP address in Russia Ivanka Trump will be an asset in her new role at the White House MORE on Saturday mocked fellow contenders Jeb Bush and Sen. Marco RubioMarco RubioOvernight Cybersecurity: Senate Intel holds Russia hearing | WH struggles to respond to latest Nunes development | Trump extends Obama cyber threat order Rubio: Former campaign aides targeted by IP address in Russia Live coverage: Senate intel holds first public Russia hearing MORE (R-Fla.) at a rally in their home state of Florida.
Trump teased Bush, a former Florida governor, for his recent decision to lay off campaign staff and cut salaries by 40 percent, and for his planned retreat with donors in Texas on Sunday.
"He's a guy wants to run our country and he can't even run his own campaign. Think of it," he added.
The billionaire business mogul also tried to draw a contrast between Bush's campaign and his, saying he has fewer campaign staff and has spent the least money of all the candidates so far.
"You have all these people, what do you need these people for?" he said. "I put up less money than everyone else, and I'm number one."
Trump is leading in Florida, according to a recent University of North Florida poll of likely Republican primary voters, with 22 percent support.
Retired neurosurgeon Ben Carson had 19 percent, while Rubio came in third with 15 percent, and Bush was fourth, with 9 percent.
"I'm not going anywhere, I'm going to stay!" Trump said. "All these people are spending money. Wouldn't it be nice to have a county that spends the least but is number one?"
The businessman also said he was amused by watching Bush and Rubio fight.
"[Rubio] was very disloyal to Bush. Everybody admits that Bush was his mentor," he said. "They're fighting like crazy. I'm laughing watching them fight."
"And he needs a lot of water on top of everything else," Trump said, in a reference Rubio's 2012 State of the Union Republican response speech where he notably took a drink of water in the middle of his speech.
"Have you ever seen a guy sweat like Rubio?" Trump asked. He also derided Carson, who in some Iowa polls is leading Trump, as "super low on energy."
"He's even lower-energy than Bush," he said.
Trump also took an indirect shot at Carson for his religion.
"I’m Presbyterian. That’s down the middle of road,” he said. “I mean, Seventh-day Adventist I don’t know about."
Carson is a Seventh-day Adventist, a Protestant denomination that believes in a literal reading of the Bible.
- Updated at 3:46 p.m.