Sen. Rand Paul (R-Ky.) hit back at Sen. John McCain (R-Ariz.) during his speech Thursday at the Conservative Political Action Conference, suggesting McCain's GOP is "stale and moss-covered."

Paul didn't actually mention McCain by name, but the reference was clear to everyone in the crowd after McCain last week labeled Paul and other members of the new generation of conservative Republicans "wacko birds."

"The GOP of old has grown stale and moss-covered," Paul said. "I don't think we need to name any names here, do we?"

Paul also offered an extensive defense of his 13-hour filibuster last week -- the same effort that drew the ire of McCain and Sen. Lindsey Graham (R-S.C.). Over the course of those 13 hours, Paul pushed the Obama administration to clarify that it wouldn't use drones against non-combatant U.S. citizens on American soil.

McCain and Graham suggested Paul's effort amounted to pointless grandstanding, with Graham even labeling him "ill-informed."

"To those who would dismiss this debate as frivolous, I say tell that to the heroic young men and women who have sacrificed their limbs and lives," Paul said. "Tell it to Sergeant J.D. Williams ... who sacrificed himself to save his fellow soldiers. Tell J.D., who lost both legs and an arm; tell him his sacrifice was great but that we had to suspend the Bill of Rights he fought for.

"Yes, the filibuster was about drones, but also about much more. Do we have a Bill of Rights or not? Do we have a Constitution or not, and will we defend it?"

Appearing immediately after another potential 2016 presidential hopeful, Sen. Marco Rubio (R-Fla.), Paul echoed Rubio by suggesting that the Republican Party doesn't need to reinvent itself, but instead get in touch with its foundational beliefs and principles.

Paul argued that the Republican Party needs to refocus itself on liberty.

"The Republican Party has to change, by going forward to the classical and timeless ideas enshrined in our Constitution," he said. "When we understand that that power corrupts and absolute power corrupts absolutely, then we will become the dominant national party again."