“We have met a crisis here in the last four years, which was a predictable crisis,” he said during a speech in December. “Many of the Austrian economists knew there was a bubble. We talked about it for a long time. And the bubble burst. It’s different this time, it is big-time different. It’s the biggest in the history of the world, what we are facing today.”

Evangelicals and social conservatives often find campaign literature on their seats before a speech starts that extols a proposal by Mr. Paul that “effectively repeals Roe v. Wade and would prevent activist judges from interfering with state decisions to protect life.”

Mr. Paul’s campaign talks are long, discursive, and bounce from place to place — he generally does not use a prepared text — but they tend to cover the same core areas: his commitment to following a strict interpretation of the Constitution and how he says that mandates a noninterventionist foreign policy; the need to constrain or eliminate the Federal Reserve; the elimination other parts of the federal government not called for by the Constitution; and a robust embrace of civil liberties that would mean repealing the Patriot Act.

Though he does not employ tested phrases that are ready made for campaign advertisements, Mr. Paul’s antiwar, anti-bailout, anti-Fed passages are the ones his audience responds to most. And while most candidates tailor their stump speeches for a local audience, Mr. Paul believes his single-minded focus on the Constitution has universal appeal.

“The Constitution is a great document,” he has said. “I have personal beliefs. I believe that individuals should have the right to their life, the right to their liberty, and also the right to keep what they earn. Fortunately for me, the Constitution and my personal beliefs come together. Because the oath of office doesn’t say, ‘Well, I’m going to go to Washington and I’m going to fulfill my personal beliefs.’ It says that we go to office and defend the Constitution against all enemies foreign and domestic.”