Opinion: Sen. Paul is Sen. Rubio's Greatest Threat

Both contenders for 2016

David Adams, a Kentucky tea party activist and former campaign manager for Sen. Rand Paul, remembers a conference call from the 2010 Senate race when the conversation turned to talk of their favorite presidents. Some said George Washington, others Abraham Lincoln. Adams pick? "Rand Paul in 2016," he recalled.

Three years later, Paul is acting like he's already preparing a future presidential campaign, courting activists from early primary states, smoothing out his positions on foreign policy, and delivering a high-profile national address, competing against a potential future GOP rival, Florida Sen. Marco Rubio.