Former Vice President Joe Biden, one of the leading Democratic presidential contenders, said on Monday that he's open to picking a Republican running mate if he were to become the party's nominee.

Biden, who often touts his history of working with Republicans, was asked by a woman at a town hall in Exeter, New Hampshire if he thought that the best way to unite the country would be to pick a Republican vice president.

"The answer is I would, but I can't think of one now,” he said, which prompted some laughter in the room. "There is some really decent Republicans that are out there still, but here's the problem right now, of the well-known ones, they've got to step up."

The comments received some swift backlash on social media, including from some prominent Democrats.

The former vice president has previously said he would prefer a vice presidential running mate who is "of color and/or a different gender."

"So, whomever I would pick for vice president, and there's a lot of qualified women, there's a lot of qualified African Americans. There really truly are. There's a plethora of really qualified people," he said. "Whomever I would pick were I fortunate enough to be your nominee, I’d pick somebody who was simpatico with me, who knew what my priorities were and knew what I wanted to do. We could disagree on tactics but strategically we'd have to be on the exact same page."

In modern politics, there has never been a bipartisan presidential ticket. In 1864, President Abraham Lincoln, a Republican, dropped his vice president at the time and choose Democrat Andrew Johnson as his running mate and went on to win the White House. The late Republican Sen. John McCain of Arizona, the GOP presidential nominee in 2008, also floated the idea of his longtime friend and former Sen. Joe Lieberman, a Democrat who became an Independent, as a possible running mate.