“As I travel across the country, the top concern of the American people is our failing economy,” Mr. Paul said in a written statement. “I look forward to working alongside Mark to solve our nation’s economic problem and to restore the American dream,” he added.

In his own statement, Mr. Spitznagel credited Mr. Paul as the only presidential candidate who understood “the destructive ramifications” of the Fed’s current policy. “I look forward to working with him on his ideas and message to change that policy,” Mr. Spitznagel said.

Mr. Spitznagel, who is 44, gained credibility for predicting two market routs over the last decade, first in 2000 and then in 2008. In the 2008 financial crisis, his Universa funds rose by 115 percent as the Standard & Poor’s 500-stock index plummeted. Mr. Spitznagel believes the next market rout is coming soon.

“There needs to be a purge,” he said in an interview with The New York Times in 2013. “If there isn’t a purge, you don’t get healthy growth.”

His thinking is shaped by the Austrian school of economics, which has its roots in 19th-century Vienna and makes the argument that the government should not meddle in any part of the economy because when it does, it causes all kinds of distortions.