"He's young, he's articulate, he clearly gave a jolt of energy to Mitt Romney yesterday," Stephanopoulos said. "Are you worried this is going to be a booster shot for the Romney campaign?"
"Well, I think it will be a booster shot within his own party," Axelrod said. "I think the Tea Party is excited. I think the social conservatives are excited."
"I really didn't think that Governor Romney would go so far to satisfy the most strident voices in his party, that he would pick someone who is so demonstrably a right-wing ideologue," Axelrod said. "But you know, I was wrong about that."
But will Ryan help Romney in crucial swing states--such as Wisconsin and Iowa--in November?
"Well, that remains to be seen," Axelrod said. "I think it helps voters clarify what this choice is about. And if what you care about is strengthening the middle class and building an economy that's meant to last ... then no, I don't think he's going to help the ticket. If you believe in a woman's right to choose, he's not going to help the ticket. But I think he will help the governor have a more convivial Republican Convention."
"I think it is a risk for President Obama to have someone like a ticket like a Romney/Ryan ticket where you have actually laid out definitive solutions and answers to America's problems," Thune said on CNN. "This president has kicked the can down the road on every major issue."
Axelrod and his fellow Democrats contend that Ryan's budget proposal--which would transform Medicare into a voucher system--will hurt Romney's chances in November. Pawlenty doesn't think so.
"I think the American people are smart, and I think the American people respect people who have real solutions to big problems," Pawlenty said. "And so Congressman Ryan and Governor Romney have put together a plan that actually tackles the problem in specific, preserves Medicare and other programs for people who are already on the program, but begins to change it in needed and realistic ways for the next generation.
Pawlenty added: "There's only one candidate in this race who's actually cut Medicare and signed such a thing into law, and that's President Obama.
Pawlenty also dismissed criticism that Romney and Ryan do not have national security and foreign policy experience.
"Don't assume that Governor Romney doesn't have foreign policy and international experience," Pawlenty said. "My goodness, he spent his entire career in global business arrangements, transactions, traveling, and understanding different countries, cultures, geography, and the like. So he gets these issues very well and probably better than the president."
"This was a defining choice for Mitt Romney," Axelrod said of Ryan. "And now it's also a clarifying choice for the American people."
Former Vermont Gov. Howard Dean agreed.
"He is going to give [Americans] a real choice," Dean said on ABC. "That's exactly what Romney was trying to avoid before. He was trying to move towards the middle, and Ryan makes it almost impossible for him to do that."