DENVER (AP) - Joe Biden and Paul Ryan are playing growing roles in the race for the White House.
The Democratic vice president and Republican Wisconsin congressman have been crisscrossing the country this week to help their No. 1s.
This is the first week both presidential candidates have running mates. Mitt Romney formally tapped Ryan on Saturday.
Biden is seen as more effective than President Barack Obama at courting white working-class voters. Ryan is a favorite of the Republican Party's conservative base, a group that long has been skeptical of Romney.
But they sometimes create headaches. Biden this week told a Virginia crowd that included hundreds of black people that Romney's plans for Wall Street would put them "back in chains."
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