The emails were released with an announcement by WikiLeaks on Twitter that linked readers to a WikiLeaks page inviting visitors to "Search the DNC email database." A search box sits underneath a one-paragraph introduction:
"Today, Friday 22 July 2016 at 10:30am EDT, WikiLeaks releases 19,252 emails and 8,034 attachments from the top of the US Democratic National Committee — part one of our new Hillary Leaks series," the introduction says. "The leaks come from the accounts of seven key figures in the DNC," including Communications Director Luis Miranda (10770 emails), National Finance Director Jordon Kaplan (3797 emails), Finance Chief of Staff Scott Comer and others. The newly released emails cover the period from January 2015 through May 25, 2016.
Friday's digital document dump follows a report last month by The Washington Post that Russian government hackers penetrated the computer network of the Democratic National Committee, gaining access to an entire database of opposition research. DNC and Clinton campaign did not respond to a request for comment Friday as reporters and campaign staff began to assess the situation.
One email written May 5 to DNC communications director Luis Miranda from another party official suggests looking at Bernie Sanders' faith.
"It might may [sic] no difference, but for KY and WVA can we get someone to ask his belief," the email from "firstname.lastname@example.org" says. "Does he believe in a God. He had skated on saying he has a Jewish heritage. I think I read he is an atheist. This could make several points difference with my peeps. My Southern Baptist peeps would draw a big difference between a Jew and an atheist."
It was well known that there had been friction between the Sanders campaign and an ostensibly impartial party apparatus.
The emails detail how bitter the relationship became, as the senator emerged as a real threat Clinton — the Democratic establishment's pick — and refused to abandon his bid as it became clear she was going to win.
The release of the emails comes at a sensitive moment, as Clinton prepares to announce her vice presidential pick and the party gets ready to gather for its national convention in Philadelphia.
One of the chief imperatives at the convention will be soothing whatever resistance remains to Clinton among the party's liberal activist wing against unifying behind her.
Sanders's supporters are crucial to Democratic hopes in the fall — both for the passion they bring to the contest, and for the vast amounts of money they are capable of raising.
An email attachment from Erik Stowe, the finance director for Northern California to Tammy Paster, a fundraising consultant, lists the benefits given to different tiers of donors to the Democratic National Convention starting next week in Philadelphia. The tiers range between a donation of $467,600 to $66,800 to the DNC, or alternatively need people to bundle a minimum of $1.25 million to $250,000 from other donors.
The top tier of donors will receive priority booking at a premier hotel in Philadelphia and free tickets to major convention events and six tickets to an "exclusive VIP party," according to the document titled, "2016 Convention Packages."
Anu Narayanswamy contributed to this report.