Former Congresswoman Gabrielle Giffords and Mark E. Kelly meet with Senators Joe Manchin (D-WV) and Pat Toomey (R-PA) on Capitol Hill concerning gun reform legislation Tuesday April 16, 2013. (Melina Mara/THE WASHINGTON POST)

It’s hard to believe that just a week ago there was talk of a thaw in Washington. Two unlikely senators had come together and created a bipartisan proposal to expand background checks. One of them, Sen. Joe Manchin III (W.Va.), a gun-owning Democrat who’d once shot a hole through a piece of legislation in a campaign ad — literally — was getting recognized as a new leader in the Senate. The other, Republican Senator Patrick Toomey (Pa.), had formerly headed the Club for Growth and been ranked as the fourth most conservative senator by National Journal.

Yet now, just a week later, the same proposal looks poised to fail. The Senate is expected to begin voting Wednesday afternoon on as many as nine gun control amendments, including the Manchin-Toomey measure. Both men have said they likely don’t have the votes for it to pass. “We will not get the votes today,” Manchin told NBC News before his office later issued a clarification. And here’s Toomey, speaking to National Review: “It’s disappointing when you put a lot of work into something, and you’re out there in a public way and it doesn’t come together.”

Of course, there are many reasons why the potential failure of the background checks measure is disappointing. First, there is the common-sense good that such a proposal could do by expanding background checks to gun-show and online sales, which are currently exempt. Moreover, given that some 91 percent of Americans (and even 85 percent of households with an NRA member) support expanded background checks, it’s more than a little disturbing that a would-be political slam dunk appears to have such an uncertain future.

But Toomey is right: It’s also disappointing that one of the few refreshing examples we’ve had recently of a bipartisan deal might, in the end, not succeed. Toomey may have acknowledged that such disappointment is part of the business of politics. But it still has to be disheartening to see something achieve support from both sides of the aisle and then still face such long odds at success.

It’s a sad but true fact in today’s hyper-partisan climate that acting in a bipartisan manner can mean putting our politicians’ conservative or liberal bona fides at risk. There is far too little incentive to work toward a bipartisan deal, particularly when appearing too moderate or too willing to work with someone on the other side is considered anathema to the base.

For proof, just consider the background checks measure itself. Toomey was worried enough about perception that he reportedly refused to publicly support the bill if he had to stand next to Sen. Charles Schumer (D-N.Y.) at a press conference. Schumer, as well as the fourth cosponsor, Sen. Mark Kirk (R-Ill.), did not attend the event announcing the deal.

Maybe the background checks amendment will squeak by somehow. But if it doesn’t, as increasingly appears likely, it may set back more than just gun control legislation. It could also set back the frequency with which our political leaders try to be part of bipartisan measures. Until more such deals actually succeed, the political calculation may be that the risk is just too high.