While President Trump has escalated pressure on Iran, even coming close to launching a military strike, most Americans want the United States to reduce tensions and return to the 2015 nuclear agreement from which Mr. Trump withdrew, according to a new poll by the Center for American Progress.

The leading contenders for the Democratic presidential nomination are on that wavelength. Most would rejoin the deal provided that Iran resumed full compliance, although there were variances in how the candidates would go about it, according to questions I sent to the candidates who rated at least 2 percent in the RealClearPolitics polling average — former Vice President Joe Biden; Senators Cory Booker, Kamala Harris, Bernie Sanders and Elizabeth Warren; Mayor Pete Buttigieg of South Bend, Ind.; and the former House member Beto O’Rourke.

All the candidates said that by breaking the deal Mr. Trump had damaged American interests and credibility, and had given Iran, which had been in full compliance, reason to inch back into nuclear activities the deal had prohibited.

“Whatever its imperfections, this was perhaps as close to a true ‘art of the deal’ as it gets” said Mr. Buttigieg. It “helped constrain the military threat that Iran poses to Israel and Europe without leading us down the path to another Middle Eastern war.”