Sen. Rand Paul, R-Ky., center, meets with members of the Londonderry Fish and Game Club in Litchfield, N.H., on Jan. 14. Paul was one of three GOP presidential hopefuls who attended Sunday's semiannual gathering of David and Charles Koch's donor network in California. Jim Cole/AP hide caption

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Sen. Rand Paul takes the stage at the Conservative Political Action Conference in National Harbor, Md., Friday. For the second consecutive year, Paul won the event's straw poll. Chip Somodevilla/Getty Images hide caption

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Sen. Rand Paul (R-Ky.) greets supporters during a tea party rally in front of the U.S. Capitol in June. Paul was a rising star in the tea party movement this year, filibustering a CIA nomination in March. Mark Wilson/Getty Images hide caption

itoggle caption Mark Wilson/Getty Images