KARL (voice-over): Cruz’s approach stands in stark contrast with fellow tea partier Rand Paul. Just days before Putin invaded Crimea, Paul said: “I think we need to have a respectful, sometimes adversarial, but a respectful relationship with Russia.”

(on camera): Senator Rand Paul said: “Some on our side are so stuck in the Cold War era, they want to tweak Russia all the time, and I don’t think that’s a good idea.” What’s your reaction to that?

CRUZ: I’m a big fan of Rand Paul. He and I are good friends. I don’t agree with him on foreign policy. I think U.S. leadership is critical in the world. And I agree with him that we should be very reluctant to deploy military force aboard. But I think there is a vital role, just as Ronald Reagan did.

When Ronald Reagan called the Soviet Union an “evil empire,” when he stood in front of the Brandenburg Gate and said, “Mr. Gorbachev, tear down this wall,” those words changed the course of history. The United States has a responsibility to defend our values.

KARL (voice-over): Senator Paul agreed to be interviewed on THIS WEEK to give his perspective, but at the last minute he backed out.