CNN has a page with several political ads from the past. The ads currently in the archives are...
From 1952...Eisenhower's "Man From Abilene" and "Eisenhower Answers America", as well as Adlai Stevenson's "Music Man" ad.
From 1960...Kennedy's "Unoriginal Nixon" ad, where Eisenhower could not come up with one original idea from then-VP Richard Nixon.
From 1964...Lyndon Johnson's "Daisy" ad, where he scared America away from Barry Goldwater.
From 1968...Hubert H. Humphrey's "Laughing at Agnew" ad...a forgotten classic.
From 1984...Ronald Reagan's "Bear In The Woods" and "Morning in America" ads, the epitome of positive campaigning and playing to one's strengths.
From 1988...George H. W. Bush's "Can We Trust Dukakis?" ads, as well as Michael Dukakis' "Quayle: Just a Heartbeat Away" ad. This campaign had a lot of negative ads on both sides. Note: I had also mistakenly attributed the "Willie Horton" ad to Bush's campaign, but it turns out that it was an independent PAC that put that out. Thanks to Brian Kirwin for the correction on American history.
Go peer back into political history!