“He’s generous,” Mr. Dacosta said, as colorful lights projected Mr. Bloomberg’s name on a wall of the National Constitution Center, where the rally was held. “I feel like it’s a nightclub in here. This is what he needs to get people going.”

The fanfare has also drawn some who don’t plan to vote for the billionaire. “Don’t get me wrong, I like Mike Bloomberg,” said Ramon Vivas, who attended Mr. Bloomberg’s Miami rally in January and wore one of the free shirts bearing that message, along with two Bloomberg buttons. “But I don’t think he’s going to get the nomination, and I support Bernie.”

Still, Mr. Vivas said he thought the Democratic Party had “moved too far to the left” and called Mr. Bloomberg a good influence on the race, adding that at other rallies he’d attended, “you typically have to pay for the T-shirts.”

The large-scale painting that Cindy Franco, the Miami artist, produced — a colorful streetscape decorated with the candidate’s name and “Miami Will Get It Done,” a variation on the campaign’s slogan — was a central backdrop for little more than an hour.

“I only had a day and a half to make it,” said Ms. Franco, who worked round the clock in the Miami warehouse with security guards provided by the campaign on hand. “They were always asking if I needed anything,” she said, declining to specify exactly how much she was paid, but adding: “It was a lot. They were very good to me.” (The campaign did not name the amount, which it will be required to report in its next federal filing.)

A virtually limitless budget

Day-to-day, some Bloomberg campaign workers with prior political experience, who requested anonymity because they were not authorized to speak about their work for Mr. Bloomberg, described what they saw as an unfathomable luxury: the ability to brainstorm and act on their ideas without concern for costs. The campaign has, for instance, hired 70 staff members in Florida and opened field offices in Puerto Rico and the United States Virgin Islands.

But being forced to think about how to stretch dollars in politics can have its advantages, Mr. Trippi said, recalling that in 2004 — when he worked for Howard Dean’s campaign, which broke the record at that time for Democratic presidential fund-raising — “a lot of the things we pioneered were exactly because we had to be that creative.”