McCain was addressing criticisms by some Republicans that the first-term Alaska governor lacks the credentials to be vice president, Politico reported Wednesday.
"She is a governor, the most popular governor in America," McCain said in an interview with talk radio host Don Imus. "I think she is the most qualified of any that has run recently for vice president."
Politico said leading conservatives, including columnists Kathleen Parker of National Review and David Brooks of The New York Times, have questioned McCain's judgment in selecting Palin as his running mate.
However, McCain said Palin has energized the Republican base.
"She has ignited our crowds," McCain said. "She has a wonderful family, a great husband, great values and she shares my worldview."