Story highlights The email was titled, "Friendly advice. No mercy."

The exchange is one of tens of thousands of emails stolen from Podesta's Gmail account and published by WikiLeaks

Washington (CNN) A hacked email exchange apparently shows Hillary Clinton's campaign chairman and a Democratic operative discussing the need to crush Vermont Sen. Bernie Sander's insurgent primary bid.

On February 21, Washington lobbyist Joel Johnson, ‎a seasoned Democratic activist who was a top White House adviser in President Bill Clinton's second term, emailed Podesta, saying Sanders "needs to be ground to a pulp."

He titled the email, "Friendly advice. No mercy."

"We can't start believing our own primary bulls---," Johnson wrote in the email. "This is no time to run the general. Crush him as hard as you can. Other than that, hope all is well and congrats on Nevada!"

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