As always, there's more than one person that has to be blamed...
The Eisenhower administration certainly created the problem. LBJ certainly vastly increased US involvement.
While LBJ vastly increased U.S involvement in Vietnam, I'd guess that pretty much every other President would have done the same thing (besides he was ignorant as far as foriegn policy went, and did what his advisors told him to do).
I blame the French for Vietnam... and Cold War paranoia... and... and... and...
The French? The French did have the good sense of pulling out in 54. (Of course they needn't have gone back in in 1945...but that's nowt to do with the cold war and all with colonialism...although that they were encouraged to do so by the Truman administration is a result of the Cold War...)
I can't really see any American politician in 1964/5 not increasing US military strength in Vietnam...not without getting skinned alive by the American media.