And candidates in Virginia and Pennsylvania won competitive races recently while supporting gun-control measures.
But gun-control activists have seen a surge in activism before, most notably after the 2012 massacre of elementary school students and their teachers in Connecticut, only to have its effect on politics fizzle.
So will this time be different? No one knows for sure, but there's evidence that the gun-control movement could be a political force this November. Here's our best attempt to gauge that:
Watch the polls
As recently as three years ago, polls showed Americans thought more guns, not fewer, was the answer to keeping communities safe. That appears to be changing significantly. Consider:
- 53 percent of Americans think the gun-control moving after Parkland will be a lasting one, according to a new Washington Post-ABC News poll.
- 57 percent think new gun laws should be politicians' priority over protecting gun rights, a jump up of more than 10 points from 2015, according to the Post-ABC poll.
- The shift is even more noticeable among younger Americans. A new Harvard University Institute of Politics poll finds 64 percent of 18-to-29-year-olds favor stricter gun laws, a 15-percentage-point jump since 2013.
- Four in 10 Americans say it is extremely important that candidates share their views on gun issues, according to the Post-ABC poll. That's higher than the number of Americans who say midterm candidates must share their views on key Washington leaders like President Trump or House Minority Leader Nancy Pelosi (D-Calif.).
But: The intractable politics of gun control has overridden public opinion in the recent past. In 2013, just months after the Sandy Hook Elementary School massacre, 50 percent of Americans felt strongly about the need to ban assault weapons, which is about where Americans are now on the ban.
A vote on that ban and on an even more popular background check bill failed in the Senate months after Sandy Hook. Today it's very unlikely this Congress takes up an assault weapons ban or any significant gun-control measures.
Watch the activism
Here's one of the big unanswered questions in the gun debate: How much of an impact will the activism of Parkland students have on an election this fall?
Gun-control activists are optimistic they can keep young people engaged, given polls show the majority of teens and their parents are concerned about mass shootings. Organizations like Everytown for Gun Safety and Giffords are launching a voter-registration effort in high schools in a number of swing states.
“There are two ways to win an election,” said Peter Ambler, the executive director of Giffords. “You either change the composition of the electorate or you change people's minds who are already voting, and I think the post-Parkland movement will be helpful on both fronts.”
But: One of the most active gun-control groups out there right now, Moms Demand Action, got started the day after the 2012 Sandy Hook shooting. Six years later, they are 4 million strong and fixtures at town halls, on the steps of state legislatures and canvassing for candidates who support gun control. The group is a powerful force in the gun-control community, but their consistent presence has yet to manifest in any sea change in the politics on guns.
Gun-control activists say these kinds of cultural shifts take time and that Moms Demand Action was an influential player in Virginia's state elections this fall. Speaking of ...
Watch what positions candidates in tough races take
One reason gun-control activists feel so optimistic about November is that a number of candidates in tough races have recently won while campaigning in support of stricter laws.
In Virginia's 2017 state elections, Democrats stomped Republicans up and down the ballot, and exit polls show guns policy was one of the top issues among voters. Those voters split evenly between the Republican and Democratic candidate for governor, which was a significant increase in turnout for the gun-control side. (Normally voters who feel strongly about guns lean heavily on the gun-rights side.)
“The intensity gap, I would say, is now DOA,” John Feinblatt, president of Everytown for Gun Safety, told The Post in November.
In a special congressional election deep in Trump country this spring, Democrat Conor Lamb won while campaigning on strengthened gun sale background checks (although he didn't think there should be new restrictions on guns).
But: There's mixed evidence that voters will continue to hold candidates' feet to the fire on gun control. A new NPR/PBS News Hour/Marist poll finds that registered voters' enthusiasm to vote based on gun policy has dropped significantly since Parkland. The poll found Democrats who say gun policy will be a major factor in whom they vote for dropped 21 points in since Parkland. With independents, it dropped 12 points.
That's far from the overwhelming public groundswell that activists on both sides say will be needed to change America's pro-gun political culture.
Watch the NRA's influence
The National Rifle Association says one of its biggest strength is its army of in-tune, motivated grass-roots supporters: One call out to them, and a politician can face mountains of letters and calls pressuring them to support gun-rights policy.
But gun-control activists think the NRA is finally starting to lose some of its grip on the politicians it counted in its camp for years. In Florida, Gov. Rick Scott (R), who is now running for Senate, broke with the NRA to sign new laws restricting gun sales. The NRA is now suing Florida.
In Ohio, term-limited Gov. John Kasich (R), who isn't ruling out a 2020 presidential bid, is supporting gun-control measures. And in Michigan, Rep. Mike Bishop (R) abruptly dropped references to his A rating from the NRA from his campaign website as he faces a potentially competitive reelection.
The NRA also spent tens of millions getting Trump elected, and he has yet to sign some of their biggest priorities into law. In addition, in the wake of Parkland, several big companies stepped back from deals with the NRA or from selling guns to people younger than 21.
But: The NRA still has a powerful grip on Congress. While its priorities haven't yet passed, no new gun-control laws have either, despite overwhelming public support for background checks and a seemingly regular slate of mass shootings.
The reality is that the NRA has had a decades-long head start on the gun-control movement, and we'll find out come November how close the gun-control movement is to closing that gap.