Mike Bloomberg’s group, Mayors Against Illegal Guns, is running ads targeting Dem Senator Mark Pryor of Arkansas over his No vote on the Manchin-Toomey compromise to expand background checks, in a sign of more attacks on red state Dems to follow. Will pressuring red state Dems over guns put the Dem Senate majority in peril?

So argues Michael Scherer of Time magazine, in a piece that seems to channel anger in Democratic circles over Bloomberg’s actions. Scherer notes that Pryor, who is up for reelection in 2014, can’t afford to lose his base, and that even the loss of one seat that might not otherwise be lost could risk the Dem majority:

The disagreement poses a dilemma for supporters of gun control for which there  is no clear answer: Is it better to teach wavering Democrats that there is a cost to voting against gun control, even if it jeopardizes Democratic control of the Senate, which is needed to enact gun control? Or is it better to maintain  Democratic Senate control even if it means that some red-state Democrats are more likely to vote against gun control to protect their right flank?

Here’s how Bloomberg’s group views this. Given the GOP’s insistence on a 60-vote Senate, gun reform is not going to pass until red state Democrats stop doing the wrong thing and voting against it. There are deeply ingrained assumptions, both among Washington pundits and strategists, and among red state Dems, that the argument over expanded background checks in particular simply can’t be won among certain voters, and that a vote against them will automatically be a political plus for Dems. These assumptions must be changed over the long haul, and the only way to do that is to extract a price for No votes — whatever the short-term consequences, even if they are dire for Dems.

“There have to be repercussions for bad votes,” Howard Wolfson, a senior adviser to Bloomberg, tells me. “Otherwise people have a  permission structure to vote that way. If there is no repercussion for voting the wrong way, why vote the right way?”

Indeed, Wolfson was quite direct in arguing that if someone like Pryor loses — the ads targeting him could, for instance, mean Dem base voters don’t turn out – it might give pause to other Dems. “You have a lot of Democrats who are unhappy with these votes. Their participation may not be robust,” Wolfson said, in a reference to the possibility of depressed base turnout. “For 20 years, Democrats were able to vote no on gun safety measures without any fear of backlash or accountability. If people who vote wrong lose in part because they voted wrong, that will send a strong signal to others.”

In addition to this, gun reform groups need to persuade red state Dems that they will not pay a price with middle of the road voters, even in red states, for supporting expanded background checks. Democrats tend to be dismissive of national polling showing overwhelming support for background checks, because they don’t believe it adequately captures the degree to which any kind of vote that can be caricatured as anti-Second Amendment will prove culturally alienating in red states. In other words, no matter what national polls say, Dems often think the argument can’t be won in red states.

But as Tom Edsall recently argued, Dem strategists and candidates tend to overestimate the conservatism of voters on such issues and underestimate their own ability to persuade them. Changing these basic assumptions is part of the longer term project envisioned by Bloomberg’s group. (See Alec MacGilliss’ excellent overview of the long term strategy, which entails spending for years to create an infrastructure to counterbalance the NRA.)

Indeed, Beltway analysts don’t talk about this, but two red state Dems up for reelection in 2014 voted for Manchin-Toomey — Kay Hagan and Mary Landrieu — and if they don’t pay a price for their vote, that should only bolster the gun reformers’ case.

“There is no question that we’re not going away,” Bloomberg adviser Wolfson tells me. “We intend to keep prosecuting the case here.” Asked how much the group would spend in the 2014 elections, he said: “It will undoubtedly be significant.”

Some Dems would prefer that Bloomberg’s group focus more heavily on gaining ground on more hospitable turf, for example by targeting vulnerable House Republicans in suburban districts in 2014 rather than red state Dems. If the group were to help knock off a few of those with a focus on gun control, that would certainly send a resounding message. Bloomberg’s group will inevitably target such Republicans, but it will also keep hitting red state Dems. Asked if more such Dems who voted against Manchin-Toomey — such as Heidi Heitkamp — will be targeted with ads, Wolfson said: “Everything is under consideration.”

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.