Missouri Democratic gubernatorial candidate Chris Koster is joining three of his Republican rivals in calling on the fourth — Eric Greitens — to return $1 million donations that he’s received from a California businessman who’s accused of keeping a woman as a sex slave for 13 years.

Greitens’ three rivals — Peter Kinder, John Brunner and Catherine Hanaway — are expected to bring up the issue during their forum tonight in Columbia, Mo.

Greitens has raised more money than the other three, with many of his largest donations coming from wealthy businessmen around the country.

So far, Greitens has indicated no plans to return the money, saying in part, “We must allow the legal process to run its course and sort out the facts.”

The businessman in question, venture capitalist Michael Goguen, was recently forced to step down from his post at Sequoia Capital after the woman filed a civil suit earlier this month.

The New York Post first reported about the suit filed by Amber Baptiste, a former stripper who contends that she was brought to the U.S. by sex traffickers when she was 15. Her suit includes lurid allegations of sexual abuse by Goguen.

Baptiste says she met Goguen in 2001, and had a relationship until 2014. She contends in the suit that Goguen reneged on a private agreement to pay her $40 million. He acknowledges paying her $10 million, and says their sexual relationship was consensual. In court documents, Goguen is accusing her of extortion.

Goguen also donated money to Republican presidential candidate John Kasich and the candidate's SuperPAC. Kasich returned the $250,000 a few days ago, after the suit became public.

Hanaway first called on Greitens to return the money on Tuesday: "I call on Mr. Greitens to cut all ties to Mr. Goguen and to send back his campaign contributions, now.  If he does not, serious questions must be raised about Mr. Greitens' judgment and whom he surrounds himself with … the seriousness of these claims against Goguen cannot be overstated … .”

On Thursday, Brunner and Kinder — and later, Koster — also weighed in.

Brunner said, in part, “We urge Mr. Greitens to do the right thing, to follow Gov. Kasich’s lead and return the money immediately. Mr. Greitens has built his campaign platform on promises of ethics reform. We do need ethics reform now, and it begins in our own backyards.”

Kinder contended, “I'm simply astounded that Eric Greitens would stand with Michael Goguen, a non-Missourian and California resident, and refuse to return funds from such a contaminated source. That kind of money has no business in Missouri. Why is Mr. Greitens, whose entire campaign is based on attacking corruption and dishonesty in politics, holding his largest donor to a lesser standard than he holds everyone else?"

Koster noted that Goguen had to leave Sequoia over the matter. “I think most Missourians will find it surprising that Mr. Greitens is relying so heavily on such a troubling person to finance his campaign,’’ Koster said.

Greitens campaign replied, “There are serious accusations being thrown around on both sides of this civil case. We must allow the legal process to run its course and sort out the facts.”

Greitens campaign also noted Hanaway’s former post as U.S. attorney for the Eastern District: “We assumed Catherine Hanaway believed folks were innocent until proven guilty. Guess not. That's a shame. Eric has fought on the front lines for our rights, and while we aren't surprised career politicians are willing to trample on them, it is disappointing nevertheless.”

Send questions and comments about this story to feedback@stlpublicradio.org.