Read Esquire's first-ever endorsement of a candidate. This article says what I believe are the most important reasons that the Republican party, the party to which I have been registered since 1994, must NOT be supported in 2008, at any level:
More than any other recent election, we are voting this year not merely for a president but to overthrow two governments. The one we can see is the one in which constitutional order has been defaced, the national spirit degraded, and the country unrecognizable because so much of the best of itself has been sold off or frittered away. The other one is the far more insidious one, a doppelgänger nation of black prisons, shredded memos, and secret justifications for even more secret crimes. Moreover, the current administration has worked hard not only to immunize itself from the political and legal consequences of the government we can see, but it has also worked within the one we cannot see in order to perpetuate itself.