Story highlights CNN's David Gregory talked to Virginia Sen. Tim Kaine about the Sanders effect on Democrats

Kaine said Trump's unpredictability has the possibility to change the electoral map

Washington (CNN) Virginia's Democratic Sen. Tim Kaine, often mentioned as a potential running mate for Hillary Clinton, warns that party discord may hurt the likely nominee of the party if unity isn't achieved soon.

In an interview for my podcast , I asked whether the Democratic primary fight has become harmful to Clinton. Kaine said, "We are getting near that point," but added he was confident Sanders and his supporters would unify. "There will be a time when he (Sanders) will be working very hard to unify the party and support Hillary."

Kaine, the former governor of a swing state, was a finalist in the veepstakes back in 2008, but predicted then he wouldn't be selected. He went on to become Democratic National Committee chairman before his election to the Senate. He's not anticipating to be on the Democratic ticket with Clinton in 2016, either.

"My gut doesn't feel much differently this time than last" he said. Kaine stressed, however, he feels this is an "existential" election with a stark choice between Clinton and presumptive Republican nominee Donald Trump.

Kaine is a key surrogate for Clinton, campaigning in the South and as part of the Clinton team's outreach to Hispanic voters. He speaks fluent Spanish and worked as a Catholic missionary in Honduras.

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