The organisation posted a tweet at around 9am on Wednesday Sydney time, with links that promised access to 678.4 megabytes of new "DNC documents".
Initial images of what appeared to be presentation slides show information about databases used for voter identification and turnout efforts.
Other slides discuss the outcome of past get-out-the-vote campaigns.
Democratic presidential candidate Hillary Clinton was US secretary of state when WikiLeaks released hundreds of thousands of State Department emails in 2010.
The latest document dump comes after an earlier tranche of emails, reportedly hacked by Guccifer 2.0, prompted the resignation of politicians within the Democratic Party on the eve of the party's convention.