He has recruited libertarian-leaning financiers and money managers from across the country, including Kenneth M. Garschina, founder of a $5.4 billion New York hedge fund and a contributor to The Review of Austrian Economics, and Donald G. Smith, an investor and board member of the Cato Institute, a libertarian research organization based in Washington. Mr. Paul’s nascent finance team includes Joe Lonsdale, a Silicon Valley venture capitalist who helped start an organization dedicated to building new sovereign cities on floating ocean platforms.

In January, Mr. Paul was the star attraction at a fund-raiser for the Goldwater Institute, a libertarian foundation and legal watchdog based in Phoenix. (Top donors were given 10 autographed copies each of the senator’s book, “Government Bullies: How Everyday Americans Are Being Harassed, Abused and Imprisoned by the Feds.”) In February, at the Club for Growth meeting, held at the Breakers resort in Florida, Mr. Paul pitched a roomful of small-government true believers on the importance of reducing prison sentences for drug offenses.

Such wealthy potential contributors could build on the army of small donors that helped make Mr. Paul’s father, former Representative Ron Paul of Texas, a successful fund-raiser in his 2008 and 2012 presidential campaigns. Many are also big donors to outside groups and “super PACs,” which will be a major force in the 2016 Republican primary. Others are primarily philanthropists in the nonprofit world — for now.