Second, you now have this very toxic intersection between terrorism and guns. I don’t know why the murder of 20 first-graders didn’t motivate this country to action, but it does seem that there has been a new wake-up call as people figure out that terrorists aren’t hijacking planes, they’re going to gun stores to buy assault weapons. So I do think that the public consciousness has been raised as they see the purposeful strategy of groups like al-Qaeda and ISIS to take advantage of our loose gun laws.

Third, I think that Hillary Clinton has something to do with it. Clinton decided to make this a defining issue of her campaign early on, and that leadership has infected the rest of the party.

“There is a reckoning coming for Republicans.”

What were the challenges that Congress faced in passing gun-control legislation after Newtown?

The anti-gun-violence movement was essentially dormant from 1994 to 2012. There was this mythology built up about the assault-weapons ban that led people to believe that dozens of Democrats lost their seats because they voted for it. That’s not actually what happened, but the proponents of gun [control] went away for 20 years, and during that time the gun lobby built up one of the nation’s most politically powerful machines.

Fast-forward to 2012 and you have an N.R.A. that is more powerful than ever and an anti-gun-violence movement that is essentially nonexistent. At some level, it is no surprise that in 2013 we lost a vote on background checks despite the fact that 90 percent of Americans supported the measure. We just fundamentally weren’t ready for that moment. That’s our challenge here: we are never going to win one of these votes unless we’ve got a political infrastructure around the country that is able to rival the gun lobby.

How close are we to the day that Congress actually passes meaningful gun-control legislation?

I think that we still have a long fight ahead. But I think that 5 or 10 years from now, people will look back at the last two weeks as a watershed moment in the history of the anti-gun-violence movement. I think this was the moment when Democrats found their voice and found their spine, and when this became an issue that you can win elections on. I don’t think that we are there yet. It is probably going to take a couple of election cycles, but I think this is a turning point.

After the Orlando shooting, Democrats made a concerted effort to tie stricter gun laws to the fight against terrorism. Why don’t Republicans buy that argument?

I think the greatest obstacle is still the power of the N.R.A. I understand that Republicans proffer this argument about due process. But they never use that argument to complain about the no-fly list. People have a constitutional right to travel, just like they have a constitutional right to own a gun. But there has never been an argument about due process before your right to fly on a plane is taken away. So there is clearly something unique within the Republican caucus about the curtailment of gun-ownership rights.

Remember that we are talking about a tiny number of people here. There are only 200 people every year on the no-fly list or the selectee list who walk into a gun store and try to buy a gun. Worst case, 10 percent or 20 percent of the names on that list are imperfect. So you are talking about a couple dozen people who would have to wait a few days to buy a gun if there was a mistake. That’s why I just don’t buy a lot of the “on-the-record” arguments for why Republicans are opposing this measure. I think it still has to do with a worry that if you get on the wrong side of the N.R.A., you might lose a primary or lose an election.