Democrats also were buoyed by his plain talk on domestic issues. He cited the Romney remark that 47 percent of Americans see themselves as "victims" dependent on government help. Biden recalled "the people I grew up with, my neighbors, they pay more effective tax than Gov. Romney pays in his federal income tax. They are elderly people who in fact are living off of Social Security."

Romney had his own mission Thursday. The former Massachusetts governor, whose patrician image got a makeover in the first debate, needed Ryan to continue marketing the brand of sensitive conservatism that Republicans are selling.

Ryan probably pleased Republicans. He stoically stuck to his talking points, refusing to be goaded by Biden’s prodding. Ryan insisted Iran was now four years closer to a nuclear weapon. No they aren’t, said Biden. “Of course they are,” said Ryan.

He repeated the Romney view that America looks weak, a dangerous sign to rogue nations. “When they see us putting daylight between ourselves and our allies in Israel, that gives them encouragement. When they see Russia watering down any further sanctions, the only reason we got a U.N. sanction is because Russia watered it down and prevented these central bank sanctions in the first place. So when they see this kind of activity, they are encouraged to continue, and that’s the problem,” he said.

Running mates occasionally make a difference in close races, most notably Lyndon Johnson’s ability to deliver Texas and its crucial electoral votes to John F. Kennedy in 1960. Ryan could swing Wisconsin, where a Quinnipiac poll taken Oct. 4-9 showed Obama up 3 points in a state once thought to be safely Democratic.

More significantly, each candidate has cemented his standing as a partisan crowd-pleaser, able to stir the faithful the way the cooler Romney and Obama often cannot.