That legal rationale for ordering limited attacks without congressional approval echoed the Obama administration’s stance during the NATO intervention in Libya in 2011. But the bombing campaign violated a limit on executive war-making powers that both Mr. Obama and Mr. Biden had said they would respect in the 2007 candidate survey.

Importantly, however, Mr. Biden said both then and now that any bombing of Iranian nuclear sites — a prospect in which the scope of unilateral presidential war-making authority has repeatedly come up — would require prior authorization from Congress because it would carry too much risk of escalation into a major war.

Still, several of Mr. Biden’s rivals took a more constrained view, suggesting that a rationale of serving American “interests” is not enough to justify even limited strikes without Congress.

“In situations where the use of force is necessary, absent an imminent threat to our national security, I will take that case to Congress and the American people to seek authorization,” former Representative Beto O’Rourke wrote.

Most candidates left the door open to using presidential signing statements, when approving bills, to claim a right to bypass provisions they see as unconstitutionally infringing on executive powers. But the answers submitted by the campaign of Senator Bernie Sanders — which were written in third person — pledged he would never use them.

“Signing statements circumvent the will of Congress and have no constitutional or legal legitimacy,” the response said. “As president, Bernie would not issue signing statements.”

The survey revealed broader disagreements about the wisdom of several other potential reforms raised by Mr. Trump’s record. Significant numbers of candidates stood on both sides of ideas like curtailing future presidents’ latitude to invoke emergency powers and to choose acting agency heads when temporarily filling vacancies.