Republican presidential nominee Donald TrumpDonald John TrumpCNN's Camerota clashes with Trump's immigration head over president's tweet LA Times editorial board labels Trump 'Bigot-in-Chief' Trump complains of 'fake polls' after surveys show him trailing multiple Democratic candidates MORE's campaign chairman said Sunday that the Democratic National Committee's (DNC) leaked emails show the party favored presumptive presidential nominee Hillary ClintonHillary Diane Rodham ClintonTrump complains of 'fake polls' after surveys show him trailing multiple Democratic candidates Hillary Clinton responds to Trump tweets telling Dem lawmakers to 'go back' to their countries The Young Turks' Cenk Uygur: Here's how to choose a president MORE from the start. 

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"What's in those emails show it was clearly a rigged system," Paul Manafort said on ABC's "This Week."

"Bernie SandersBernie SandersTrump complains of 'fake polls' after surveys show him trailing multiple Democratic candidates The Hill's Morning Report - Presented by JUUL Labs - Trump attack on progressive Dems draws sharp rebuke Judd Gregg: Counting the costs of Democrats' desires MORE never had a chance, and frankly, I think you're going to see some of that resentment boil over this week [at the Democratic National Convention] in Philly." 

Emails from within the DNC leaked by WikiLeaks Friday showed party officials privately planned how to undermine the Vermont senator's presidential campaign. 

In one May 21 email, DNC press secretary Mark Paustenbach writes to communications director Luis Miranda about planting a narrative to the media that Sanders’s “campaign was a mess.”

"The establishment and the special interests picked their candidate, Hillary Clinton, and made sure nothing the people were going to do or say were going to interfere with her selection," Manafort said Sunday.