With talk about the ads we have seen lately, I figured I would post this. Historians have agreed that McCain's attacks are par for the course.
Historians say McCain camp not sleaziest - David Mark and Avi Zenilman - Politico.com

There is also a site that has campaign ads/commercials dating back to 1952.
The Living Room Candidate - Commercials - 1952 - Ike for President