Kinder, a Republican from Cape Girardeau, is expected to run for governor next year against Democratic incumbent Jay Nixon.
On Wednesday, Kinder told the story of his involvement with Tammy Chapman to the St. Louis Post-Dispatch. He said a recent photograph with her at a St. Louis bar advertising "pantless" servers, was the result of a chance meeting when he stopped there to use the bathroom.
Kinder acknowledged his relationship with her was closer in the past. It happened 17 years ago when he was a member of the state Senate.
"As a young single man, 17 years ago, I made a foolish choice," Kinder, now 57, said. "I had no thought that I would run for any statewide office, much less possibly run for governor someday."
Kinder has already repaid the state $52,000 in expenses he received for stays in St. Louis to attend Tea Party and social events.