New Jersey Democratic honcho Joe Cryan had a tumultuous three-year relationship with a pretty former Jon Corzine staffer — and then used his powerful post to push stalking charges on her, sensational court papers claim.

Cryan, the New Jersey state Democratic chairman, allegedly dashed off “countless sexually explicit and pornographic e-mails” to former lobbyist and Senate campaign worker Karen Golding, according to the papers.

In one missive, Cryan allegedly wrote about “inviting her to his office and having her under his desk performing sexual acts.”

Cryan, 49, who is also a state assemblyman and Union County undersheriff, allegedly sent the e-mails from his government office and computers, according to papers filed by Golding, a 40-year-old blonde, in Morris County Superior Court and seen by Page Six.

Golding claims the “mostly sexual” relationship lasted three years until 2006 — when they got together for intimate dinners and sleepovers at political powwows in Boston and Atlantic City, and resulted in a “traumatic abortion” in 2004.

Golding’s papers describe how Cryan allegedly denied a relationship and painted her as “a disturbed individual living in a lovesick fantasy world.”

Golding was busted in 2006 for stalking him and another woman. (Corzine posted Golding’s $5,000 bail but later apologized, calling it a lapse in judgment. )

Golding pleaded guilty — but now she wants the conviction overturned, claiming she was railroaded into it.

According to the filing, her plea was “coerced” by state prosecutors who “blindly accept[ed]” Cryan’s word and never told Golding she could have the case presented to a grand jury.

“Mr. Cryan did not have an intimate relationship with Karen Golding,” prosecutors on her stalking case said in a separate filing earlier this year. “There certainly was no relationship lasting 2½ years where a child was conceived.”