1960s Nixon definitely. He epitomized the 60s.
How so? Nixon was President for less than one year in the 1960s.
IMO the answer would be Reagan.
Nixon was one of the most famous and influential people throughout the 60's, in or out of office.
He never quit running for President between 1960 and 1968.
His run for California governor was just practice, then?
When Nixon ran for Governor in 1962, he promised not to run for President in 1964.
But he still never quit planning for his comeback to run for President in 1968.
And I should clarify, Nixon epitomized the late 60s and early 70s.
I can agree with that.
A problem with this question is that decades don't line up nicely with Presidential terms. It's also true that a one-term President will almost certainly be less of a defining influence than a two-termer. It's no surprise that the three that have been most commonly mentioned (Eisenhower, Reagan, and Clinton) were two-term Presidents whose tenures were mostly contained within a single decade.
You almost have to feel bad for Bush Sr lol. If somebody asks who was president in the 80's,you would answer Reagan, or Clinton for the 90's. Because Bush Sr was president in the late 80's and early 90's, he is now mostly historical non entity to non political nerds. Interestingly enough, if Bush Sr had won in 1992, then he would be the 90's president as well serving from 1989-1997.