(CNN) – Artur Davis, the former four-term Democratic congressman from Alabama who co-chaired President Barack Obama's 2008 campaign, introduced the running mate of Obama's Republican challenger in Virginia Friday.
"Are you ready to meet the next vice president of the United States?" Davis asked at a rally in Springfield, Virginia. It was Ryan's second event of the day. He held a rally outside Richmond on Friday morning.
In his introduction, Davis pointed to Ryan's age – he's 42 – as having energized the GOP. Davis is 44.
"Remember a week ago, some of our Democratic friends had the illusion that we were kind of an older party. That were the party of the last generation. One week later I'm the oldest man on this stage right now," Davis said. "What a difference a week makes."
Davis, who said in May he was switching parties from Democrat to Republican, said he had only disagreed with Ryan on one subject: the status of Led Zeppelin as the "#1 band of the modern era."
"I questioned you as you said it. As a Genesis man, I questioned it," Davis said.
He also praised Ryan's willingness to advance a House GOP budget that included sometimes-unpopular cuts to programs in the name of cutting the federal debt.
"President Romney is going to have a vice president who believes, in a town where no one takes responsibility for anything, Washington D.C., this man wrote a budget with tough, hard, necessary choices. He put his name on it," Davis said.