After a string of critical losses in the 2008 Democratic primary, Hillary Clinton's campaign put out a hard-hitting ad that questioned Barack Obama's readiness for the White House.

Future "warm and fuzzy" ads can trace their lineage to this one. For his reelection campaign, Ronald Reagan employed a team of advertising all-stars, resulting in one of the most famous catchphrases in American politics.

The infamous Willie Horton ad placed a nail in the coffin of Michael Dukakis' 1988 presidential run.

In the 2012 Republican primary, Herman Cain's campaign produced an unusual video featuring Cain's chief of staff, Mark Block, giving a pep talk while smoking a cigarette.

In 2007, long-shot Democratic candidate Mike Gravel released one of the strangest ads in political history.

Perhaps the most famous political ad of all time, this early television spot ran on air just once, but generated enough media coverage to become a real factor in the 1964 presidential election.