According to Wikipedia, Barry Morris Goldwater was a businessman and five-term United States Senator from Arizona and the Republican Party's nominee for president in the 1964 election. Personally, I find his involvement to be quite extensive with the five terms serving as Senator, so I would say he was a major figure in American politics.
Senator Barry Goldwater excised considerable influence and power in US politics during his five terms as an Arizona Senator. His authorship of the Goldwater-Nichols Act of 1986 was responsible for changing how the US armed forces fight by altering the chain of command from the President to the Secretary of Defense directly to the Unified Combatant Commands. This change reduced the ability of civilians to dictate military response in combat regions.
Yes, Barry is definately considered one of the most major figures in the 20th century politics. He served as a senator for five terms, which is a long time to be re voted into an office. Also he was the republican candidate for president in the 1964 presidential election, but lost.
As a major presidential candidate and one of the longest serving Congressmen of the era, there's no other way to describe Barry Goldwater. He was a major figure in our 20th century American politics. He represents a time when I wasn't embarrassed to tell people I was from Arizona (thanks a lot Tea Party idiots).
No, Barry Goldwater cannot be considered a major figure in American politics of the 20th century, because he did not win the presidential election for which he was nominated. Candidates for the presidency who lose the election are more or less done with their political relevance and their careers. Goldwater did not accomplish anything particularly noteworthy.