From Michael Bloomberg’s point of view, appealing to New Yorkers not to give any more campaign money directly or indirectly to Democratic senators who voted against the incredibly modest Manchin-Toomey background check legislation is pretty much a no-brainer. Democratic donors are obviously going to be more sympathetic to the gun safety clause than Republican donors. A pro-NRA vote this bad might even become an issue in a Democratic as opposed to a Republican primary. And from Bloomberg’s general “plague on both houses” political posture towards the two major parties, counter-balancing the power of the NRA and elevating the profile of the gun issue is a lot more important than the identity of the party controlling the Senate.

Besides, Bloomberg’s Mayors Against Illegal Guns has already crossed the line by running ads in Arkansas against one of his primary targets (those running for re-eleciton next year), Mark Pryor. And since Pryor’s already using Bloomberg’s criticism as a positive credential in his own ads, you could argue the mayor is reinforcing a general principle of encouraging Democratic unity on the gun issue without inflicting any specific damage on the putative objects of a “purge.”

Still, it’s going to be hard for the Democratic donors receiving those missives to forget two relevant facts: (1) Pryor and the other target, Mark Begich, are by most accounts the Democratic senators most vulnerable to defeat in 2014, and a donor boycott will probably hurt them a lot more than any direct attacks by Michael Bloomberg; and (2) the likely Republican opponents for both men (Joe Miller in Alaska and Tom Cotton in Arkansas) happen to be almost medieval in their aggressive advocacy of conservative ideology as the eternal answer to every question (with the answer on anything affecting gun rights being “No!”).

My own feeling is that the best way to convince southern and western Democrats to stop treating issues like gun safety as cultural totems requiring them to get as far to the right as possible is to show that sensible positions on those issues are not, actually, career-killers. The re-election of Mary Landrieu and Kay Hagan, southern Democrats who did support Manchin-Toomey, will do more for the cause Bloomberg espouses than all the trouble he can create for Begich and Pryor. Mayors Against Illegal Guns ran ads in Louisiana and North Carolina urging Landrieu and Hagan to vote the way they did, so perhaps they should show some gratitude and offer to red-state Democrats a carrot as well as a stick.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.