Mr. Paul bristles at an adjective often used to describe his foreign policy: isolationist. “Not only am I for being involved, I’m actually for more involvement than the neocons,” he said, referring to the branch of conservatism that supports an interventionist foreign policy.

“The neocons are really neoisolationists,” he added, “in the sense that they are so hardened — that everybody should behave like us, and everybody in the world should be in our image — that they discount the concept of looking at things realistically and negotiating with people who don’t have our point of view.”

Mr. Paul often complains that his worldview is caricatured by people who are eager to cast him as a clone of his father, former Representative Ron Paul of Texas, who is deeply suspicious of American involvement overseas. “They start out with a mischaracterization of his point of view, bastardize it, make it worse,” the senator said.

Mr. Paul said he believes that war should be fought only when Congress authorizes it and that President Obama has overstepped his constitutional authority in using drones as a substitute for traditional military forces. Though Mr. Paul has been accused of having a weak policy of containment for dealing with Iran, he has insisted that his reluctance to publicly discuss the idea of a military strike there stems from his unwillingness to broadcast options to the nation’s enemies.

This less swaggering approach has won him applause as he has toured the country, visiting places like Berkeley, Calif., recently, and Cambridge, Mass. It dovetails with his efforts to rein in what he sees as examples of a runaway, unchecked executive branch that flouts the Constitution by spying on its citizens and fighting covert wars with drones.

Mr. Paul may not have a long record on foreign policy — as he often points out, he was a full-time ophthalmologist until just three and a half years ago — but his votes in the Senate on bills dealing with Israel and Iran, along with past statements dug up and disseminated by his opponents, have raised concern among those with hawkish tendencies.

He believes that all foreign aid should be eventually cut off. His description of aid to Israel as “welfare” in a 2011 interview alarmed some Jewish conservatives.