It's not just men throwing women under the bus, so to speak.
Women do it to other women, and men to it to other men, and women do it to men.
Case of a Man Being Used in this Fashion: When Stephane Dion became leader of the Liberals.
The movers and shakers in the Liberal Party knew he could not win a federal election, but they scapegoated him in order to divert public attention from the corruption in the party. (Sponsorship scandal anyone?) The tactic seems to have worked.