Biden ran for the Democratic presidential nomination in 2008, dropping out after finishing fifth in the Iowa caucuses. He also mounted an unsuccessful bid for the 1988 Democratic nomination.
Biden seemed to call out Rep. Paul RyanPaul RyanPelosi: 'Of course' Dems can be against abortion Five fights for Trump’s first year Sunday shows preview: Trump stares down 100-day mark MORE (R-Wis.), Mitt Romney's running mate, on Monday. The vice president, eating Wisconsin cheese soup, said he wanted Ryan to know about his meal.
Biden has occasionally stirred controversy during the 2012 campaign. In August, he drew fire from Republicans for telling a mixed-race audience that the GOP would "put y'all back in chains" by rolling back President Obama's Wall Street reforms if Democrats lose in November.
At the time, Obama sought to quell rumors that Biden could be replaced on the Democratic presidential ticket by Secretary of State Hillary ClintonHillary Rodham ClintonPoll: 85 percent of Clinton supporters would vote for her again OMB director: Government shutdown not a 'desired end' Poll: Almost half say Trump off to poor start MORE. Obama called Biden an "outstanding" vice president.