The question from Chuck Todd to Senator Elizabeth Warren was direct: “What do you do about the hundreds of millions of guns already out there, and does the federal government have to play a role in dealing with them?” It was an effective query, one that, arguably, cuts to the heart of America’s gun problem, which claimed nearly forty thousand lives last year. A 2017 study estimated that there are three hundred and ninety-three million civilian-owned firearms in the United States, a rate of 120.5 guns for every hundred residents, twice that of the second-highest nation, Yemen. Yet Warren, who has been battling with Senator Bernie Sanders to win over the Democratic Party’s left wing, sidestepped the question. She offered up a quotable sound bite—“Gun violence is a national health emergency in this country, and we need to treat it like that”—and talked about the need to “double down on research,” an allusion to how the N.R.A. succeeded, during the mid-nineteen-nineties, in effectively cutting off federal funding for gun-violence research. Yet she was unwilling, even after Todd probed her a second time, to raise the possibility of policies like the mandatory gun-buyback program that Australia undertook two decades ago, after a devastating mass shooting, which was found to be effective in reducing gun deaths. Gun-control advocates have made undeniable strides in this country over the last few years, but Warren’s caution on the issue was a reminder of how politically fraught the issue remains, at least in the eyes of some candidates.