lizbeth: This campaign, it seems to me, is much more subtly dirty than most, within my memory.
May I suggest a Harry Lorayne memory course?
Presidential and Congressional campaigns have been this dirty, both subtly and overtly, since Nixon. (And the campaigns pre-1900 were absolutely vicious in their vitriol against opposing candidates.)
Nixon loved to smear enemies with the "Commie" brush. Neither Dems nor Reps are guilt free on this, there is no moral high ground, the party operatives will say whatever they have to say in order to win.
Sometimes they're found out and their candidate is punished for it, but simple lies that instill racial and economic fear and resentment in people usually work.
Racially speaking, the Dems are quick to point out any racial "slip" by a Republican, such as the "macaca" remark which may have cost Sen. George Allen the presidential nominataion, etc.
Republicans, since they can't use race against a white candidate, usually try to make the dems look as dorky as possible, i.e. the Dukakis tank pic, Kerry hunting and windsurfing, etc. (I'll bet Kerry never shot a friend in the face while hunting). Or they play the fear card, such as the Willy Horton ad.
In the current election, Republicans can't come right out and say "He's black, don't vote for him." so they frame it with talk of his middle name, his non-American background (untrue) and so on. McCain's appearances of late have included the pledge of allegiance (are we in school?) the Star Spangled Banner, and America the Beautiful, which many people think is our National Anthem. Nothing wrong with any of those, except when they are so cynically used to convey the idea that Obama is not as American as McCain. It's like McCain beating Obama over the head with an American flag.
Fear has always worked for Republicans. There is no reason for them to discontinue their attempts to scare us, in order to win an election. And since racism is based on fear, they're doing a pretty good job.