The American voter has changed very much since the 1950's. The voter turn out rate has declined since that time and it is mostly due to just a few factors. Some of these is lack of trust in the government and the eventual not wanting to decide which person should represent them. The lack of choices in elections plays a major role in the low voter turn out. In a lot of elections the candidates are not that good and the advertising campaigns from the opponents may have made the candidate look bad.
The American voter in 1950 had more trust in the candidates that were running, its not that the candidates weren't as corrupt and bad as many of today's are, its juts that the media at the time had more respect for public officials and didn't cover all of the scandals that we have today. The Average voter in 1950 also wasn't as busy as today's voters are.
In the 1950's the average voter tended to have stronger views and party distinctions then they do today.
Overall the evolution of dirty campaigns and the busier lifestyle of today have led to less voter turnout and a crowd that is more independent.