It's the final countdown.

In just a few hours, Republican presidential candidate Donald Trump will face off against Democratic Hillary Clinton in the third and final debate of this campaign cycle.

And while their matchups are certainly unique (and definitely must see TV--the first event set a record as the most watched debate ever), the events have become a rite of passage for candidates over the past few decades.

Take a look at the clips below to relive some memorable candidate moments below.