The Democrats All Disagree With Trump on Iran. Then It Gets Mushy.

The six Democratic presidential candidates who debated Tuesday night in Des Moines agreed on one point: President Trump threw away a nuclear deal that was working and is now recklessly speeding toward war with Iran.

But they all turned vague when pressed on how they would accomplish their key goals — preventing Tehran from obtaining nuclear capability, stopping the revival of the Islamic State and disarming North Korea — without backing up diplomacy with the threat of military force.

Time and again, they separated themselves from Mr. Trump, especially on his rejection of allies and his unilateral action to pull out of international treaties and agreements. But they ended up describing a series of hopes for a return to negotiations and plans for incremental withdrawals that at moments echoed the Trump administration, circa 2019.

And all the candidates struggled to define the conditions under which they might use military force if there were no imminent threat, rejecting Mr. Trump’s “America First” approach to the world but trying to avoid stoking fears that they lacked the spine and strategic sensibilities to succeed as commander in chief.