(CNN) - There aren't that many people who can easily give a $2.5 million political donation, but count former New York City Mayor Michael Bloomberg among them.
CNN confirmed Tuesday that Bloomberg, who last week finished his third term running New York City, donated $2.5 million to Senate Majority PAC, a super PAC dedicated to helping Democrats keep control of the chamber. The Democrats currently have a 55-45 majority in the Senate, but are defending 21 of the 35 seats up for grabs in November's midterm elections.
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Bloomberg, a Democrat-turned-Republican-turned-independent, has pushed for increased gun control laws through Mayors Against Illegal Guns, a group[ he co-founded eight years ago, and last year poured more than $5 million into Independence USA PAC, which he set up in 2012. The group spent heavily last year in a special U.S. House election in the Chicago area where gun control was a major issue.
Separately, Bloomberg last year also donated $1 million each to Democrats Cory Booker in his special Senate election victory in New Jersey and Terry McAuliffe in his gubernatorial win in Virginia.
Bloomberg, whose personal fortune is estimated at over $25 billion, is one of the richest men in the world.
The new donation, first reported by Politico, sparked speculation that the move could be the start of numerous contributions by Bloomberg during the 2014 midterm cycle.
While many of Bloomberg's donations have gone to Democratic candidates and causes, Stu Loeser, an adviser to Bloomberg who served as a former chief spokesman for the mayor told CNN that "Bloomberg may also continue to support Republican candidates who take tough stands he agrees with."
The Senate Majority PAC would not comment on reports of the donation, and by law doesn't have to release its next fundraising report until the end of the month.
So far this cycle the PAC has already gone up with ads in defense of Sens. Mark Begich of Alaska, Kay Hagan of North Carolina, Mary Landrieu of Louisiana and Mark Pryor of Arkansas, who all face challenging re-elections this November. But the PAC's spending pales in comparison to the big bucks already spent against Democratic senators by Americans for Prosperity, a conservative group backed by the billionaire industrialist Koch brothers.
"Democrats are playing mostly defense in this year's Senate races and $2.5 million is a significant amount of money, which will help them defend some of the most important states," Nathan Gonzales, deputy editor of the non-partisan Rothenberg Political Report, told CNN.
But while money is a major factor, Gonzales notes that "when it comes to the top Senate races, I don't think they will be decided by money. Millions of dollars will be spent by both sides. The races will ultimately be decided by the candidates, the messages, and the national environment."