Humphreys called for Missouri Lt. Gov. Peter Kinder (R) to resign last year over a scandal involving a former stripper. He was unsuccessful; Kinder just survived a primary challenge from a Humphreys-backed candidate.
There's reportedly a push to get Ann Wagner, the Republican running for Todd Akin's House seat, to take his place in the Senate race. That way, Akin could still run for Congress without mucking things up too much for the GOP.