2016 not far off at crucial conservative conference

Four possible 2016 GOP White House hopefuls will speak at this year's Conservative Political Action Conference, a popular cattle call for Republicans considering bids for the White House.

CNN has learned that 2012 GOP presidential candidate Rick Santorum will address CPAC. A senior adviser to the former two-term senator from Pennsylvania says Santorum has accepted an invitation to speak at the conference, which this year will be held March 14-16.

And the American Conservative Union, which organizes the annual conference, announced Thursday that Sen. Marco Rubio of Florida, who was elected to the Senate in 2010 with strong support from tea party activists, will give an address at the event.

Last week the American Conservative Union announced that Rep. Paul Ryan of Wisconsin, the House Budget Committee chairman and last year's Republican vice presidential nominee, will be a featured speaker at the gathering. And earlier this week CNN confirmed that Sen. Rand Paul of Kentucky will also speak at conference.

CPAC is the largest annual gathering of conservative leaders and activists, and it's boosted the presidential campaigns, or ambitions, of many Republican candidates. The annual CPAC GOP presidential nomination straw poll is considered a key gauge of conservative sentiment, and garners much media attention.

Santorum was once considered a long shot for the 2012 GOP nomination, but he ended up coming out on top in the Iowa caucuses and battled eventual nominee Mitt Romney deep into the primary season last year. After dropping out, Santorum launched "Patriot Voices," a nonprofit advocacy group that pushes for conservative causes and candidates.

Santorum, who was very popular with social conservative voters during the primary season, has hinted that he may make another run for the White House. "I'm open to that possibility," the Republican said when asked about a 2016 presidential bid in late November on CNN's "Piers Morgan Tonight."

ACU Chairman Al Cardenas praised Rubio, saying "my friend Marco Rubio has quickly become one of our nation's most prominent conservative leaders. Senator Rubio's participation will serve as motivation to CPAC attendees and conservatives across the country to take action and bring our country back on track."

CPAC, which turns 40 this year, will be held for the first time at the Gaylord National Resort and Convention Center just outside Washington, in Prince George's County, Maryland. For years the conference was held at the Marriott Wardman Park hotel in the nation's capital.