Powell is a moderate Republican who obviously cares more about his country than about supporting his party no matter how badly it behaves.

He's telling his fellow Republicans in a very no-nonsense way to knock off the stupid crap about Ayers, comments like "palling around with terrorists", unchallenged insinuations about "being a Muslim" or pointlessly calling Obama a Socialist, and get serious about addressing and discussing the nation's problems in a more responsible manner.

Powell won't convince anyone on the right wing - he has no friends there - but he's very respected and admired by many moderate Republicans and Independants, and his endorsement of Obama will definitely have an impact. The remaining undecided vote may be small at this stage of the race, but I think a big chunk of it could be swayed by Colin Powell's endorsement, and especially his straightforward, common sense, down-to-earth explanation for it. In addition to the undecideds, he may even convince a few Republicans who support McCain to switch to Obama.