A lot of attention is rightly being paid to Robin Kelly’s Democratic primary victory over “gun rights” pol Debbie Halvorson in Chicago’s second district last night. Michael Bloomberg’s PAC spent big on gun control ads in the race to prove that there is a financial counterweight to the NRA out there — and that opposition to gun reform can be turned into a serious political liability. It worked.

But there’s another layer of broad significance to Kelly’s victory that shouldn’t go overlooked: Specifically, that liberal groups are now going to try to make gun control a litmus test issue in Democratic primaries. This was a first test case, and you can expect that they will now be looking to primary “gun rights” Dems and make them pay a price for coziness with the NRA wherever possible.

Bloomberg’s PAC wasn’t the only group that sought to swing the race. A number of liberal organizations and online groups also got involved: CREDO Super PAC did on the ground organizing against Halvorson; DailyKos raised money for her; Democracy for America also raised money and contributed phone banking; and the Progressive Change Campaign Committee did some last minute organizing. The success of this effort is likely to encourage such groups to look for other “gun rights” Dems to target.

“As long as Democrats and Republicans keep voting with the NRA instead of their constituents, you will see progressive groups like CREDO, DFA and the Daily Kos community continue to make the NRA a major factor in our election organizing — including in Democratic primaries — going forward,” Becky Bond, the president of the CREDO Super PAC, tells me.

Obviously it remains to be seen how widespread this effort will be in practice. The conditions have to be right to fund a primary. It is still unclear whether opposition to gun reform can be turned into a liability for Dems in red states or marginal districts that don’t look all that much like the district in which Kelly won last night. But the mere fact that these groups are now talking about looking for “gun rights” Dems to primary alone underscores how much of a shift we’re seeing when it comes to gun politics.

There seems to be a genuine and growing sense among Dems that gun reform is now good politics for them. Part of this is because of country’s changing demographics and the changing nature of the Dem coalition. As Obama’s victory showed, the Democratic Party is increasingly reliant on groups that are growing as a share of the electorate — minorities, young voters, and suburban and college educated whites, especially women — that view gun control as a priority. At the same time, Dems are increasingly less reliant on constituencies — blue collar white men, rural voters — who are hostile towards stricter gun laws, and no longer see as much of a need to shape the party’s agenda to avoid alienating them.

On the national level, you can see this dynamic playing out in the jockeying in advance of the 2016 Democratic presidential primary. At least two expected contenders — New York Governor Andrew Cuomo and Maryland Governor Martin O’Malley — responded to the Newtown shooting by rolling out aggressive gun control packages. This signals a calculation that gun control has become a priority for Democratic constituencies — and doesn’t necessarily imperil a Democrat’s national ambitions in a general election, either.

It remains to be seen how much gun control will resonate in various states and individual House districts, but the mere fact that liberal groups are going to try to hold “gun rights” Dems accountable is a good sign as to which way the politics of guns is shifting.

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