New York Mayor Michael R. Bloomberg is asking big-money donors to withhold contributions to Democratic senators who voted against stricter gun-control laws.

New York Mayor Michael I. Bloomberg. (Seth Wenig/AP)

Bloomberg is sending a letter to more than 1,000 top New York-area campaign donors on Wednesday specifically urging them not to contribute to four Senate Democrats -- Max Baucus (Mont.), Mark Begich (Alaska), Heidi Heitkamp (N.D.) and Mark Pryor (Ark.) -- who voted against a bipartisan gun bill that failed to advance in the Senate.

By asking campaign donors to withhold funds, the mayor -- who also has deep pockets -- is going against the will of his congressional Democratic allies who tried, but failed to advance gun legislation in April and have warned that increased public criticism of vulnerable Democratic lawmakers could lead to Republican gains.

The Senate failed to advance a bipartisan bill that would have expanded the national gun background check system in April, when supporters fell short of the 60 votes necessary to proceed to final debate. In the weeks since, Bloomberg's anti-gun group, Mayors Against Illegal Guns, has spent hundreds of thousands of dollars targeting several senators of both parties for voting against the measure.

"Instead of rising above politics to pass a law that would save lives," Bloomberg, a political independent, wrote, the four senators "sided with a gun lobby increasingly out of touch with Americans' priorities."

"The next time these four senators want you to support them with donations to their campaigns, tell them you cannot," Bloomberg wrote. "Until they show that they will stand up for the American people and not the gun lobby, tell them you cannot support their candidacy."

Sen. Michael Bennet (D-Colo.), who chairs the Democratic Senatorial Campaign Committee and is responsible for promoting Democratic gains during next year's midterm elections, defended his colleagues against Bloomberg's efforts Wednesday morning by calling the Democratic senators "very strong candidates." But he stopped short of criticizing Bloomberg directly.

"Mayor Bloomberg is entitled to make choices he wants to make, he obviously feels very strongly about this issue and he has for a long time and I’m not going to make a judgment about that. He’s entitled to do what he feels he needs to do," Bennet said at a breakfast meeting hosted by the Christian Science Monitor.

Begich and Pryor face difficult races next year, while Heitkamp is a freshman and wouldn't face reelection until 2018. Baucus has announced plans to retire. A spokesman for Begich declined to comment, while a Heitkamp spokesman said the senator would have no comment. A Baucus spokeswoman said that "the only thing that ever influences Senator Baucus' policy decisions is what's right for Montana and what he hears from his constituents back home. Campaign contributions have never and will never influence Senator Baucus' decisions on any legislation."

Pryor is trying to use Bloomberg's criticisms to his advantage by airing a campaign ad that highlights his opposition to the gun bill. “The mayor of New York City is running ads against me because I opposed President Obama’s gun-control legislation,” Pryor says in the ad. He later adds that "no one from New York or Washington tells me what to do; I listen to Arkansas.”

But John Feinblatt, Bloomberg's chief policy adviser in New York, struck back sharply at Pryor's tactics Wednesday morning.

"I think that certainly when senators push back and say they’re not going to take directions from New York, they ought to stop the hypocrisy, because they clearly like to listen to New Yorkers when it comes time to scoop up their donations," Feinblatt told reporters on a conference call. "They ought to address what’s on the minds of voters and constituents and explain why they chose to take a vote that was in direct conflict with the people they represent."

Bloomberg's personal appeal to campaign donors comes as several parents of some of the youngest victims of gun violence are scheduled to meet this week with lawmakers on Capitol Hill. Parents of children killed during the mass shooting at Sandy Hook Elementary School in Newtown, Conn. last December plan to meet Wednesday with Sen. Joe Manchin III (D-W. Va.), the lead sponsor of the defeated gun bill, and House Speaker John A. Boehner (R-Ohio).

Read Bloomberg's complete letter to donors below:

On April 17, four Democrats joined with most Senate Republicans in voting "no" on the Manchin-Toomey background checks compromise, legislation that would have strengthened public safety by tightening loopholes in our current gun laws that allow felons and the dangerously mentally ill to get guns without passing a background check. Instead of rising above politics to pass a law that would save lives, these four Senators—Max Baucus of Montana, Mark Begich of Alaska, Heidi Heitkamp of North Dakota, and Mark Pryor of Arkansas—sided with a gun lobby increasingly out of touch with Americans' priorities.

I am writing to ask you: the next time these four Senators want you to support them with donations to their campaigns, tell them you cannot. Until they show that they will stand up for the American people and not the gun lobby, tell them you cannot support their candidacy. These "no" votes were a slap in the face to Americans everywhere. Polls consistently show that 90% of Americans—including 82% of gun owners and 74% of NRA members—support requiring background checks for all gun sales so that illegal guns do not fall into the hands of criminals and the dangerously mentally ill. But instead of standing up for what's right, and for a common-sense measure their constituents support, these Senators made a calculated vote designed to pander to the gun lobby in anticipation of their next election.

When confronted with a tough vote, we expect our leaders to show courage and support the interests of the American people—and many of them did. The background checks compromise was fashioned by two NRA "A"-rated Senators, Joe Manchin (D) of West Virginia and Pat Toomey (R) of Pennsylvania, who bridged the partisan divide crippling the Senate to offer bipartisan legislation that strengthens the federal background check system. Most Senators, including Senators from states with strong traditions of gun ownership, rose to the occasion by supporting the Manchin-Toomey compromise. They understand that closing loopholes that make it easy for felons to buy guns will not weaken gun rights one bit.

But the background checks compromise still fell short of the 60 votes it needed to pass. Senators Baucus, Begich, Heitkamp, and Pryor sided with the minority, reminding us of why so many people are angry at Congress. 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.

By voting against background checks, these Senators told us they would rather bow down to a special interest group than support a common-sense measure to help law enforcement fight gun crime. Now you can tell these Senators: by voting against background checks, they voted against your values and your family's safety. And until they show they will stop bowing to pressure from the gun lobby, you should not support them.


Michael R. Bloomberg

This item has been updated to reflect that Heitkamp doesn't face reelection until 2018.

Read more:

In politics, Mayor Bloomberg operates as a party of one

Bloomberg wants to change the gun lobby

How Howard Wolfson went from Team Clinton to Team Bloomberg

Follow Ed O'Keefe on Twitter: @edatpost