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 RyanRyan: Graham-Cassidy 'best, last chance' to repeal ObamaCare Ryan: Americans want to see Trump talking with Dem leaders Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea 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.

"I tell you what," Biden said. "I’d like you to know that you could let the congressman [know] I’m eating Wisconsin cheese soup."

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 Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE. Obama called Biden an "outstanding" vice president.