Forensic Files episode title “The Black Widow”?
From Wikipedia: "McCaskill was married to David Exposito, with whom she had three children. The couple divorced in 1995, after 11 years of marriage, while McCaskill was Jackson County Prosecutor. David Exposito was found murdered in Kansas City, Kansas on December 12, 2005. Exposito's murder has never been solved."
She was State Auditor when her husband was murdered. It would be pretty easy for an ex-County Prosecutor to get some ex-con to do him away for her.
Here's an FR thread from 2005 regarding his murder:
(Claire) McCaskill's ex-husband is found murdered (Missouri State Auditor)