For anyone following gun control (or gun safety) as a political issue, it would be easy to dismiss 2016 as just another year when a whole lot happened, but nothing changed. 

There have been more than 200 mass shootings in the United States so far this year, including the massacre at the Pulse nightclub in Orlando and the July attack on Dallas police officers. After every major incident, Washington followed the now-familiar script of outrage, calls from Democrats for gun restrictions, denial from Republicans that guns are the problem, and then, as usual, gridlock.

But as Election Day gets closer, an incremental, but important shift has modified gun safety as a typically partisan campaign issue. A handful of Republicans in must-win Senate seats are now running on their willingness to embrace even modest gun reforms, while outside interest groups are crossing the aisle to reward those Republicans for doing so.

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The highest profile Republican who may be changing the rules on guns is Sen. Patrick J. Toomey, who is locked in a dead-heat race in Pennsylvania against Katie McGinty. Toomey blazed into the Senate in 2010 as an unapologetic conservative and former president of the Club for Growth, with an A rating from the National Rifle Association. So it was striking when he joined West Virginia Democratic Sen. Joe Manchin, after the shootings at Sandy Hook Elementary School in 2012, to sponsor legislation to expand background checks for firearms purchases.

Toomey joined Democrats last year on a similar bill after the San Bernardino shootings and voted over the summer on a GOP proposal to crosscheck gun purchases against the terrorist watch list.

The Washington politics on guns may be complicated for Toomey, but attitudes on the issue at home in Pennsylvania are unambiguous. A PPP poll of the state in August showed 87 percent of all Key State voters in favor of background checks on all gun purchases, including 84 percent of Republicans.

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The issue is usually a potent partisan issue for Democrats, who typically portray Republicans as puppets of the gun lobby, but Toomey’s decision to sponsor and vote for gun restrictions has made that almost impossible for McGinty, especially after PACs led by Gabby Giffords and former New York Mayor Michael Bloomberg endorsed Toomey in recent weeks.

Bloomberg’s group, Independence USA, is running nearly $750,000 of ads in the Philadelphia suburbs, where Toomey has to perform well to win re-election. An especially powerful ad features the daughter of the Sandy Hook principal, who was killed protecting children at her school.

“Pat Toomey crossed party lines to do the right thing,” she says. 

In an op-ed for CNN, Giffords and her husband Mark Kelly praised both Toomey and Illinois Republican Sen. Mark Kirk as principled on the issue that nearly cost the former Arizona congresswoman her life when she was shot outside a supermarket during a 2011 constituent meeting.

The endorsement came at a pivotal time for Kirk, who trails Democratic Rep. Tammy Duckworth and must receive crossover support in a state which is even more in favor of tougher gun laws than the rest of the country. Kirk has long been on the outs with the NRA. More important for him is Gifford’s praise of him as an independent pragmatist, a reputation Kirk has been working to push.

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In all-important Florida, guns have become a crucial issue in that state’s Senate race. Sen. Marco Rubio said the Pulse nightclub shooting so moved him that he decided to run for another term.

Last week, Rubio introduced legislation to notify the FBI if the subject of a federal terrorism investigation in the last 10 years tries to buy a gun. Rubio’s Democratic opponent, Rep. Patrick Murphy, dismissed the bill as an effort to “paper over” a weak record, but it’s astonishing, nonetheless, to see a conservative Republican introduce a gun bill less than two months before Election Day. 

In 1994, the assault weapons ban was blamed as the reason dozens of Democrats lost their seats. In 2016, a similar decision by Republicans may be the reason some Republicans keep their jobs. If that’s the result, 2016 will end up being the year the politics of guns changed, no matter what legislation ended up passing on Capitol Hill.