PHILADELPHIA — Republican National Committee Chairman Reince Priebus said Sunday the resignation of his Democratic counterpart was "inevitable" given the exposure of the party's preference for Hillary Clinton over her primary opponent, Sen. Bernie Sanders, when internal emails were leaked on Friday.

"I know firsthand how hard it is being chair of a national party, but when you rig a system ... I think this kind of outcome is inevitable, and there is no way out," Priebus said at an RNC event held here just one day before the Democratic National Committee kicked off its own convention.

"I think that today's events show, I think, really what an uphill climb the Democrats are facing this week," he added.

The RNC chairman highlighted the divisions among Democrats that were opened up by Clinton's selection of Virginia Sen. Tim Kaine as her running mate.

Priebus called Kaine "the furthest thing from an olive branch" for supporters of Bernie Sanders who may still be skeptical of Clinton's commitment to progressivism.

The conference came hours after Democratic National Committee Chairwoman Debbie Wasserman Schultz announced her decision to resign at the end of the convention on Thursday. Emails published by Wikileaks on Friday indicated she had attempted to stifle Sanders' popularity by conspiring with other DNC officials to question his religious beliefs.

Paul Manafort, Donald Trump's campaign manager, took the stage in a converted boxing arena Sunday evening to attack Kaine's record as former governor of Virginia. He also laid out a plan of attack against Bill Clinton, who is set to speak Tuesday. Manafort said Hillary Clinton has acted as an "enabler" for some of his past behavior.

Trump's campaign manager said the hack of the DNC server that ultimately felled Wasserman Schultz meant Hillary Clinton's private server was hacked as well.

"We take every precaution you can imagine," RNC Chair Priebus said of protecting the RNC's data. "You don't see articles about [RNC] leaked emails."