From XKCD [http://xkcd.com/1686/].
Which misstates the case a little bit. This is the first presidential election (in the US) in which there are voters who were born after 9/11. Arguably last go-around there were voters who were too young to appreciate or understand the impact of 9/11 when it happened, or what the US was like beforehand.
[UPDATE: Math is hard. 18-year-olds this year were born (roughly) in 1998, which would have made them 3 when 9/11 occurred. Last election, there were 7yos, which is arguably also too young to remember.]
Regardless of that nitpicking, it's a worthwhile sea change. The changes in the US — the legitimization of the Security State, the demonization of Islam as the existential enemy of the US, the Iraq and Afghanistan Wars — all of these things are major differences between Then and Now. For some first-time voters, they have always been part of the background noise of the country they grew up in, something that is accepted as the status quo. The idea of meeting your party at the gate at the airport is as foreign as standing at the dock while someone's ocean liner comes in.
And don't get me started on the Cold War.
This is not to say this is a bad or a good thing, just that it is a very distinct and real thing, a shift in the gestalt of the nation, of assumptions as to what is normal and what is not, of the perception of What Things Used To Be Like.
It's weird and unsettling, but reality is often that way.
Police states work like that…soon it just becomes normal.
You can't vote at 15, can you?
+Colm Buckley Well, it's a lot easier to if you have voting registrars who are as bad at math as I apparently am. (Corrected).
+Stan Pedzick Any social change operates that way. And, fwiw, that also works for good things. There are mutiple generations now that have grown up under (e.g.) interracial marriages being legal nation-wide, such that more and more (though not totally, by any means) it doesn't cause any eyelash-batting.
But, yes, negative things become the New Normal too.