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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Rubio, seen here addressing the National Press Club in May, told NPR he'll decide on a presidential run in the next few months Alex Wong/Getty hide caption

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From left, Sen. Jeff Flake, R-Ariz., Sen. Chuck Schumer, D-NY, Sen. John McCain, R-Ariz., and Sen. Michael Bennett, D-Colo, arrive at a news conference after their tour of the Mexico border with the United States on Wednesday in Nogales, Ariz. The senators are part of the "Gang of Eight," a larger group of legislators collaborating on changes to immigration. Ross D. Franklin/AP hide caption

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Can our nation afford political waffling on issues of scientific consensus? Stan Honda/AFP/Getty Images hide caption

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Florida U.S. Senate candidates Marco Rubio (from left), Charlie Crist and Kendrick Meek share a laugh before their debate Wednesday. Joe Burbank, Pool/AP hide caption

itoggle caption Joe Burbank, Pool/AP