“I have no fucking idea,” one Republican strategist told me recently, when I asked how he was gaming out the gun issue ahead of the midterm elections. He was referring, of course, to the politics of gun rights, a winning issue for the Republicans for at least 25 years, which have been scrambled by the recent massacre at Marjory Stoneman Douglas High School in Parkland, Florida, and its dramatic aftermath.

The alleged perpetrator, a troubled 19-year-old with a history of making violent threats, murdered 14 students and three educators with a legally purchased, semi-automatic weapon. For weeks thereafter, the surviving, media-savvy teenagers staged demonstrations to ensure that the media did not soon forget about the horror, which might have otherwise drifted from the news cycle. Even Donald Trump expressed regret with the current state of gun-safety laws under consideration. Partly as a result, voters across the country, particularly in upscale suburbs like Parkland, want the federal government to do something. And many of these voters, it just so happens, are Republicans, those historically inclined to vote Republican, or swing voters. They also happen to live in the two dozen or so battleground districts that could determine the fate of the G.O.P.’s 24-seat House majority in November. For the first time in memory, guns could be a vulnerability for the Republican Party.

Many G.O.P. strategists assumed long ago that guns would never be a problem for their party. After all, it had not become one even after Columbine, in 1999 (13 murdered); Sandy Hook, in 2012 (28 murdered); Orlando, in 2016 (49 murdered); or Las Vegas, last October (58 murdered). But this time around, the Parkland tragedy has occurred at a politically fraught moment for the G.O.P., as it searches for a foothold in suburban battlegrounds, which are fiscally conservative and hawkish on national security, but not animated by Trump’s brash cultural conservatism that holds currency in blue-collar communities across the heartland. In these districts, already in danger of turning blue because of deep dissatisfaction with the president’s polarizing leadership, towing the party line or ignoring guns altogether is no longer acceptable. As Republican Rep. Ryan Costello, who represents a targeted suburban Philadelphia district, told me for an article in the Washington Examiner, parents are worried for their children’s safety. Falling back on a defense of the constitutional right to keep and bear arms, and waxing philosophical that “guns don’t kill people; people kill people,” isn’t going to cut it. “The gun-safety issue, or movement, is much more organized, much more effective,” Costello said. And so Republican insiders are being compelled to adapt.

But what to do, exactly? Republicans are still trying to figure out the answer—both in terms of the politics and the substance. One Republican media consultant put it more pointedly. “You’re going to have to have something affirmative that you can be for,” this person said. And what would that something affirmative be? It’s unclear, but one Republican adviser who specializes in running tough suburban campaigns suggested that G.O.P. candidates follow Trump’s lead as they mull the question. The president, as is often his wont, has tried to have it both ways on gun rights. He campaigned on his commitment to the Second Amendment, warning voters that Hillary Clinton was coming for their guns. Meanwhile, Trump received overwhelming grassroots and financial support from the National Rifle Association, possibly the most respected advocacy group among Republican primary voters. But post-Parkland, Trump called for strengthening federal background checks, raising the age limit to purchase certain weapons, and beefing up restrictions to prevent the mentally ill from obtaining firearms.