The Museum of the Moving Image has a very cool site where you can view dozens of presidential campaign television advertisements from the last 56 years.
One thing you notice right away from even the earliest spots is that attack ads have been around since the very advent of television. One difference is that candidates used to have the guts to deliver the attacks themselves, like Ike in this 1952 ad: (Sorry, WordPress won’t let me embed flash video from the site)
I also think some of the Lyndon Johnson ads unleashed against Goldwater make today’s spots look tame. If you’re a political junkie, like I am, you can easily lose a couple hours at this site, especially on a slow September Friday. It’s also sort of comforting to remember that the nation has survived other knock-down, drag-out election fights.