Didn’t this guy tell reporters he was moving on to other issues after the big background-checks flameout last week? What happened?

Senators Joe Manchin III, Democrat of West Virginia, and Patrick J. Toomey, Republican of Pennsylvania, have been talking in recent days about how they could persuade more senators to support their bill to expand background checks for gun buyers, which drew backing from only four Republicans last week.

“We’re going to work it hard,” Mr. Manchin said Thursday, adding that he was looking at tweaking the language of his bill in a way that he believed would satisfy senators who, for example, felt that background checks on person-to-person gun sales would be too onerous for people who live in rural areas far from a sporting goods store.

Those concerns were an issue for Alaska’s senators, Lisa Murkowski, a Republican, and Mark Begich, a Democrat.

So, what happened? This happened:

Sen. Pat Toomey’s job rating is at a record high following the Pennsylvania Republican’s sponsorship of legislation to expand gun background checks, according to a poll released Friday.

Pennsylvania voters approved of Toomey’s performance by a margin of 48 percent to 30 percent, up a net 7 points from March, the Quinnipiac University survey reports…

Background checks are supported by 85 percent of Pennsylvania’s voters. More than half, including a majority of Democrats and four in 10 Republicans, said that Toomey’s co-sponsorship of a bipartisan background check bill improved their opinion of him. Just 12 percent said they saw him less favorably.

Background checks are popular generally, and as a Republican from a bluish state (the Mark Pryor problem in reverse) he’s looking for ways to pander to the center. Even if nothing ends up passing, he can’t waste an opportunity to remind Pennsylvanians that he’s working hard on a high-profile issue with bipartisan support. Let’s look closer at the numbers, though. Per Quinnipiac, 54 percent of PA voters think more favorably of him for working on the bill with Manchin versus just 12 percent who don’t, which is what you’d expect to see given that support for expanded background checks usually polls north of 85 percent. But what does that mean in terms of bottom-line job approval?

Compare that to his numbers from March:

The good news for him? He hasn’t lost any Republican support for backing a new gun-control bill, although some undecideds have moved into the disapprove column. He can live with that; the goal here is not to be primaried and he’s on his way towards that goal with 58 percent GOP approval. The bad news? A big chunk of his new support is coming from a 10-point swing among Democrats that’ll surely evaporate as he gets closer to reelection in 2016. He’s up with independents too, which is more significant because it’s potentially more durable, but background-checks alone won’t preserve it. He has to build a more comprehensive reputation for bipartisanship to sell himself as a “reasonable” Republican in his next campaign, which means more compromises to come. How many will Pennsylvania conservatives tolerate before they get restless?

One other X factor here is that the Toomey/Manchin bill failed, of course. What would these numbers have looked like if it had passed? More support for Toomey because he proved he could get something done, or less support among Republicans if/when unintended consequences from the bill started being publicized among conservatives? What if, a year from now, Obama and Biden tried for another round of more aggressive gun control and cited Toomey specifically, and repeatedly, as an example of a Republican who supported “common sense” regulations? Would conservatives hold him responsible for enabling the next wave of slippery-slope gun regs? The whole trick here for Toomey is knowing how far he can go before he risks a backlash on the right. Background checks are probably safe (Kelly Ayotte’s getting hammered in purplish New Hampshire for voting no on Toomey’s bill), but any further and he’s in peril.

Update: Via National Journal, Democrats do have a litmus-test issue for swing-state senators — but, contra Joe Scarborough, it ain’t gun control.

Many progressive activists say Democratic incumbents will face a sterner backlash if they support cutting entitlement programs like Social Security and Medicare. That’s potentially critical because Obama has already publicly supported a plan for switching to a so-called “chained CPI” for Social Security benefits that could become a centerpiece of a major deficit-reduction deal.

“A vote against our safety net will rate higher than [the gun-control vote],” said Markos Moulitsas, a liberal activist and commentator. “We consider protecting our social net to be a core Democratic issue. If you don’t believe in doing that, I don’t understand why you’d even be a Democrat. And given how popular Social Security and Medicare are, it’s not as if it’s politically courageous to support those programs.”…

“Anyone up in 2014, and really any Democrat period, needs to know, if they do vote to cut Social Security, Medicare, or Medicaid benefits, it’s going to be a clarion call to the entire progressive community,” [Sroka] said. “It will fire up the grassroots base of Democratic Party.”

Think a fiscal conservative like Toomey will be able to hang on to his new Democratic support when entitlement reform finally blows up?