Republican presidential nominee Donald TrumpDonald John TrumpTrump watching 'very closely' as Portland braces for dueling protests WaPo calls Trump admin 'another threat' to endangered species Are Democrats turning Trump-like? 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 ClintonAre Democrats turning Trump-like? The Hill's Campaign Report: Battle for Senate begins to take shape The Hill's Morning Report — Trump and the new Israel-'squad' controversy 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 SandersVolatile presidential polls spark new round of anxieties GOP memo deflects some gun questions to 'violence from the left' British Bookmaker: Warren has replaced Biden as Democratic primary favorite 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.