But the most consistent theme of the day, from the moment Mr. Bloomberg entered the casual D’Egg Diner, painted in subdued orange and off-white, was the financial firepower he has brought to the Democratic Party and some of its favorite causes.

Mr. Bloomberg, who is one of the wealthiest men in the country, entered the diner with Nancy Guy, a newly elected Virginia state legislator whose candidacy Mr. Bloomberg supported this fall. He noted to a reporter that the Virginia legislature had flipped this month from Republican to Democratic control, and that he had been able to “help in that process.”

Speaking to reporters at a nearby Hilton soon after, Mr. Bloomberg noted he had spent “hundreds of millions of dollars fighting the N.R.A.,” including considerable “monies that we provided on gun safety” in Virginia’s recent elections, and had used his fortune to take on the coal and tobacco industries. He named two members of Congress from Virginia, Representatives Elaine Luria and Jennifer Wexton, whose campaigns he supported and spent heavily on in 2018.

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Ms. Guy, who introduced Mr. Bloomberg at the Hilton, did not quite endorse the former mayor, but she began by thanking a Bloomberg-backed environmental group, Beyond Carbon — “and its founder, Michael Bloomberg” — for its spending in her campaign. Ms. Guy noted that climate issues were particularly salient in her coastal district, and Mr. Bloomberg’s money “probably contributed to my victory, so I’m deeply appreciative.”

“For years, I’ve been using my resources for the things that matter to me,” Mr. Bloomberg said, noting that those causes included gun control and arresting climate change.

That avalanche of money has led several Democratic presidential candidates to point to Mr. Bloomberg’s campaign as an emblem of a broken system. In Ankeny, Iowa, on Monday, Ms. Warren derided Mr. Bloomberg as a wealthy interloper seeking to “buy a nomination in the Democratic Party,” and she urged voters to show that his approach would fail.