Todd Young

As he contemplated how to respond to President Trump’s escalating war in Iran, Senator Todd Young of Indiana looked at his menu of options and found few satisfying choices.

For years, he had warned of the dangers of a legislative branch that had ceded its war-making powers to the executive branch. He had routinely teamed with Democrats in efforts to repeal authorizations for combat operations against Iraq and to urge a restoration of Congress’s “proper constitutional role on questions of war and peace.”

But on Wednesday, Mr. Young, a 53-year-old former Marine, joined all but one of his Republican colleagues in opposing a measure that would limit Mr. Trump’s power to continue waging war against Iran without congressional authorization.

Despite harboring deep qualms about his institution’s role in reasserting its prerogatives, Mr. Young said his decision reflected the unwieldy military reality that Mr. Trump had thrust upon the nation when he decided unilaterally to carry out sweeping strikes against Iran, and the apparent lack of appetite among his colleagues in Congress to reclaim their war-making authorities.

“We fell short institutionally in rising to the moment,” Mr. Young said in an interview, noting that Mr. Trump had made clear that he was weighing an attack on Iran if its leaders failed to meet his demands in negotiations to rein in its nuclear program, and yet Congress still did nothing.

“And so here we are, now that we’re actually in a war, figuring out answers to our questions, trying to elicit just basic facts about political objectives, and, more importantly, trying to unify the American people around those objectives,” he said. “And I feel like much of this could have been done, and should have been done, beforehand.”

Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber? Log in.

Want all of The Times? Subscribe.