http://blog.lib.umn.edu/cspg/smartpolitics/2012/11/death_of_the_battlegrounds_the.php
The national race was very close, yet only 5 states were decided by 5 points or less. Things sure have changed a lot since 1976, when we had a whopping 20 states with margins of 5 points or less....including California, Texas, and New York. Imagine how wild that race would have been to follow if modern polling and the internet had existed back then.
The country is also a lot more polarized today so if everyone around you despises a certain party/ideology, there is a good chance you will fall in line. Also lets remember back then a 10 point swing over a month's period was not uncommon whereas today you will notice only a small number of voters swung between parties; generally the Democrats and Republicans had a firm 47% base who would vote for them no matter what and only 6% up for grabs, whereas back then the number of firm supporters was likely under 40% for both parties.
