While the interest of the media is focused on the candidates, political scientists should look at the tectonic shift under way in the American electorate. Seven years of Bush Administration have played the role of midwife to a new coalition of groups that is making the party younger, more affluent, more liberal, and more responsive to women, Latinos, and African-Americans. Of course, many of these constituencies were heavily tilted toward the Democrats already in the 1970s, but what is new is the growth of Latinos, and there commitment to the Democratic party. It is worth noting that still in 2004 Republicans scored some successes among them, playing the religious card (most of them are catholic, and traditionalist).
This shift, well described in a recent National Journal article, can be measured both by looking at the participation in the democratic primaries so far and by checking the polls about party affiliation.
We already noticed the surprisingly large turnout on the Democratic side ("Let's Crunch Some Numbers", below) but now Edison Media Research and Mitofsky International polls offer evidence that in 18 the states where it is possible to compare 2004 and 2008 caucuses and primaries, the share of the vote cast by young people has risen by substantial margins. Women's share of the vote has grown in 17 of the 18 states, albeit by smaller increments because the "gender gap" was already significant. In 12 of those states, Latinos have cast a larger percentage of votes, as have the voters who consider themselves liberals. African-Americans have boosted their share in 11 of the 18 states. Look at this chart, courtesy of National Journal, that shows how the movement was under way already in 2006.