Impalin

a word used to describe any example of an instance where a politician makes a move that should be politically (and solely politically) beneficial but backfires. Most recent, this term has been used in discussion of McCain’s choice to nominate Sarah Palin as his VP.

Past tense: "impalined"

John McCain will feel silly for impalin‘ himself with that VP pick!
I hope the Republicans get mad at John McCain for his impalin‘ decision to choose Governor Palin.
He lost the election by impalin‘ himself because he made that single decision.