But less consensus exists on what to do with the assault weapons that Americans already own: All the candidates support some kind of program in which the government would buy weapons back from gun owners, but none of the three leading Democrats — Mr. Biden, Ms. Warren or Mr. Sanders — support making that program mandatory. Seven in 10 Democratic voters support mandatory buybacks, according to an August Quinnipiac poll, although less than half of all voters do.

There is a similar lack of consensus among the Democratic candidates on whether to force all gun owners to register their weapons in a national database. Democratic politicians long dismissed the idea of a gun registry as a fear-mongering tactic from the National Rifle Association, but it now enjoys broad support from the public: 62 percent of Americans back the idea, including 85 percent of Democrats.

Most candidates now favor establishing a registry, though some — including Mayor Pete Buttigieg of South Bend, Ind. — do not. Others, like Mr. Biden and Mr. Sanders, say it should apply only to owners of assault weapons.

Climate Change









Democratic voters widely believe that climate change represents an international emergency — 84 percent said so in the August Quinnipiac poll — and roughly nine in 10 think the United States is not doing enough to address global warming.

All the major Democratic candidates have expressed support for the Green New Deal, though some have been more guarded than others. All five senators who will debate Tuesday night co-sponsored the bill. Mr. Buttigieg has simply called it “the right beginning,” while Mr. Biden’s campaign website endorses it as a “crucial framework.”

But the Green New Deal enjoys broad support from the American public, with 63 percent of respondents to an NPR/PBS NewsHour/Marist poll in July saying they like the idea of investing government money to fund sustainable infrastructure projects and green jobs. Among Democrats, it’s a particularly winning concept; 86 percent of Democrats nationwide back the Green New Deal, the poll found.