Bloomberg sent out more than 1,000 personal letters, The Washington Post reported. He targeted U.S. Sens. Max Baucus of Montana, Mark Begich of Alaska, Heidi Heitkamp of North Dakota and Mark Pryor of Arkansas.
In his letter, Bloomberg said many senators from states where support for gun rights is high supported the compromise bill put forward by Joe Manchin, D-W.Va., and Pat Toomey, R-Pa. The mayor said the four Democrats he named helped ensure the bill fell short of the 60 votes needed to get it to the Senate floor.
"Senators Baucus, Begich, Heitkamp and Pryor sided with the minority, reminding us of why so many people are angry at Congress," Bloomberg said. "Astonishingly, the four senators did this even as they ask New Yorkers, who contributed a significant share of the funding for their last election bids, to donate to them once again. Their votes were an affront to the nation. Make no mistake: Loopholes at the federal level undermine our efforts to keep our streets safe."
Bloomberg's action could hurt Begich and Pryor, who are up for re-election next year. Baucus plans to retire, while Heitkamp, who was elected to the Senate last year, does not face the voters until 2018.