In a statement released by Rubio’s camp, Armey called Rubio “a champion of freedom and an inspiring leader for the next generation of the conservative movement. His track record and conservative convictions are a breath of fresh air in a party looking for new leaders to advance the principles of limited government, lower taxes and economic liberty.”

Rubio, a fiscal and social conservative, is running to the right of Florida Gov. Charlie Crist (R) in the high-profile primary. He has already picked up a few notable Republican endorsements in former Arkansas Gov. Mike Huckabee, Sen. Jim DeMint (S.C.) and Rep. Jeff Miller (Fla.).

But he’s certainly the underdog in the primary fight. Crist has earned the endorsement of Sen. Mel Martinez (R-Fla.) — who he and Rubio hope to replace next year — as well as the National Republican Senatorial Committee and most of the GOP establishment in Washington, D.C., and Florida GOP Reps. Lincoln Diaz-Balart and Mario Diaz-Balart.

But, perhaps more importantly, Crist has proven to be a powerful fundraiser. He reported $4.3 million in receipts in just 50 days of fundraising. Rubio brought in just $340,000 in the second quarter.

“Our campaign isn’t about who raises the most money, or who’s the most famous or who’s the best known,” Rubio said on Monday. “It’s about the notion that ideas in politics need to matter. And that the only way the Republican Party is going to find itself back in the majority is standing for specific ideas that people say those things are relevant to their day-to-day lives.”