Cut and Thrust by Stuart Woods

In Cut and Thrust, lawyer and bon vivant Stone Barrington is actively involved in First Lady Kate Lee's campaign for the presidency. The book mostly focuses on activities at the convention, where Kate is trying to fight off several challengers for the nomination. There's also a subplot about the certifiable ex-wife of Stone's friend Ed Eagle, who has dedicated her life to killing off Ed.

It's not your typical Stone Barrington book. But it is an interesting story. And if Kate Lee indeed wins the presidency, it could take this series in a different direction since she and Stone are such good pals and because he's dating the woman who would be Kate's chief of staff.