Tanden, the president of the liberal think tank Center for American Progress, emailed Clinton's campaign chairman
John Podesta in March 2015 after news broke that Clinton used a private email server during her tenure as Secretary of State.
"Why didn't they get this stuff out like 18 months ago? So crazy," Tanden wrote to Podesta in March 2015, referencing Clinton's campaign.
Tanden then referenced Cheryl Mills, one of Clinton's top aides at the time, writing in another email, "This is a cheryl special. Know you love her, but this stuff is like her Achilles heal (sic). Or kryptonite. she just can't say no to this sh--. Why didn't they get this stuff out like 18 months ago? So crazy."
"I guess I know the answer," Tanden wrote back. "They wanted to get away with it."
Neither Tanden nor the Clinton campaign immediately responded to requests for comment.
And then in an another email, Tanden wrote, "a thought that I'm sure has occurred to you hours ago: the archives request them and she complies immediately (avoids subpeonas) don't yell at me."
These emails are part of a wider hack of Podesta's emails published by WikiLeaks. The group has released emails hacked from Podesta's private gmail account daily for more than two weeks. The Clinton campaign has refused to confirm or deny specific emails' authenticity and has accused the Russian government of being behind their theft and release -- a claim WikiLeaks and the Russians have denied.
It appears that Tanden was asking why Mills and the other top aide didn't automatically send Clinton's emails to the archives instead of trying to find a way not to hand them over to protect Clinton.
CNN cannot independently confirm the emails' authenticity. But the Clinton campaign has not challenged any emails in other WikiLeaks releases.
Many of the emails released by WikiLeaks have focused on the fallout from Clinton's private email server use. The campaign team and top aides were involved in lengthy email threads gaming out the response, from statements to the media, to responses to congressional inquiries, to even tweets on the topic.
Tanden had also been a frequent character in the emails. As president of CAP and veteran of Obama and Clinton world, Tanden represented a progressive flank of the party and had a close relationship with Podesta, who helped found and lead CAP before stepping down in 2011.
In the emails, she frequently used colorful language to describe opponents of the campaign on the left, right or in the media, and also sometimes had criticisms of the candidate or campaign itself, though she described herself as a "loyal soldier" for Clinton.