Every four years you hear presidential candidates say that this year's election is about the future not the past. Hillary Clinton says it every time she speaks to blunt the criticism, as Bob Shrum, the political consultant (now retired) has noted, that she is running a nostalgia campaign.

What have social scientists found? For half a century they have studied elections scientifically and for that same period they have always come up with the same answer. Elections are always about the past.

Even when a campaign seems to be about the future it's about the past.

Say a candidate (Obama?) comes to town and tells your friends and neighbors he offers a new politics (whatever that means). That sounds like somebody selling you something about the future. But what he is really selling you is hope. And he is selling you hope because he knows a lot of people, demoralized by Bush administration incompetence over the past six and a half years, are out of hope. That is to say, he is telling you the future won't be like the past. Translation: the election is about the past.

As I wrote in a post in October 2006 in the run-up to the congressional elections:

People don't vote for something so much as they vote against something.

Elections are referendums on the past. As V.O. Key noted in The Responsible Electorate (1966):

"Critics of the American party system fret because the minority party does not play the role of an imaginative advocate heralding the shape of a new world. In truth, it gains votes most notably from among those groups who are disappointed by, who disapprove of, or who regard themselves as injured by, the actions of the Administration. The opposition can maximize its strength as it centers its fire on those elements of the Administration program disliked by the largest numbers of people."

It's useful to remember what elections are really about as we head into the 2008 campaign. Much as we wish to escape to the future the past keeps holding us back. The candidate who nurses carefully the grudges Americans hold is likely to have a powerful claim on their affections.