By Rhodes Cook - July 17, 2008

Speculation abounds these days about whether this fall's presidential election will produce a dramatically different electoral map than the virtually static one of the last two contests. Will Colorado and Virginia lead an array of longtime Republican states that might be won this time by Democrat Barack Obama? Or might Michigan and Pennsylvania be in the vanguard of Democratic strongholds picked off by Republican John McCain?

Those are among the more intriguing questions as the 2008 general election campaign heats up. But one thing's for sure: changes in the electoral map require some alterations in the electorate itself. And that seems to be happening.

In the 29 states (plus the District of Columbia) where voter affiliation is kept by party, the Democrats have scored perceptible gains since the presidential election of 2004 while the Republicans have suffered significant losses. To be specific, the number of registered Democrats in party registration states has grown by nearly 700,000 since President George W. Bush was reelected in November 2004, while the total of registered Republicans has declined by almost 1 million.

To be sure, the changes have taken place within a huge pool of voters that totals 96 million in the party registration states. In short, even with the loss of nearly a million voters, the number of registered Republicans is still 97 percent as large as it was at the time of President Bush's reelection.

Yet this overall trend--Democrats up, Republicans down--is also mirrored in many of the states that already have been identified as battlegrounds for 2008. And with only a comparative handful of votes needed to swing key states such as Iowa and Nevada the Democrats' way, the latest registration numbers can only fuel the party's considerable optimism.

There are a variety of reasons why the Democrats are gaining new voters, starting with demographic change. In fast-growing Nevada, for instance, a 4,400-vote registration advantage for the Republicans in November 2004 has been transformed into an imposing registration edge of more than 55,000 for the Democrats. That represents nearly three times Bush's margin of victory in Nevada four years ago.

In states that voted near the end of the primary calendar this spring, the spirited Democratic contest between Obama and Hillary Clinton brought tens of thousands of new voters into the party's ranks. In Pennsylvania, there was a Democratic registration surge of more than 300,000 in the six months between November 2007 and the April presidential primary. In Oregon, Democratic registrations increased by more than 100,000 between last November and the May primary. In both states, which went narrowly for Democrat John Kerry in 2004, the number of registered Republicans conspicuously dropped during the same per.

And there are states where Democratic gains seem related less to the excitement of the recent Clinton-Obama contest than to the general nature of the times - in which President Bush enjoys little support beyond the GOP base and the appeal of the Republican "brand" is questioned even by party loyalists.

Case in point: Iowa. At the time of the state's precinct caucuses in early January, the number of registered Democrats across the state was essentially unchanged from the 2004 election. But in the months since the caucuses, Democratic registrations have surged by nearly 70,000, while the Republicans have gained barely 7,000 voters - all this in a state that Bush carried in 2004 by barely 10,000 votes.

The same Democratic registration trend is evident on an even larger scale in California. Since the state's presidential primary in early February, Democratic registrations have mushroomed - growing by more than 300,000, while Republican registrations have increased by just 15,000. The disparity underscores why California's 55 electoral votes should be safely found once again in the Democratic column this fall.

To make matters worse for the Republicans, they continue to follow the path to obscurity in much of the Northeast, an area of the country where just a half century ago the GOP's then-large moderate wing was rooted. Nowadays, barely one quarter of all registered voters in New York are Republicans. In Massachusetts and Rhode Island, the GOP share now is down to 12 percent or less.

The saving grace for Republicans is that this does not appear to be a "base" election like the two won by George W. Bush. In 2000 and particularly 2004, both parties emphasized registering and turning out their own voters. This time, independents will be extremely important - a group that comprises roughly a quarter of the voters in party registration states. McCain's longtime appeal to independents gives him an opportunity to offset losses caused by a shrinking GOP base.

Voter registration tallies will be updated on a regular basis between now and the election as both parties and their allies become fully engaged in registering new voters. But in a campaign that is already uphill for McCain and the Republicans, this is another important area where they will be playing catch up.