Small changes can have dramatic consequences. The electorate shifted about 4 points toward the Democrats in between the 2004 and 2008 elections--from 48.3 percent of the popular vote four years ago to 52.5 percent today. But those 4 points gave Obama the largest share of the vote since 1988, the best showing by a Democrat since 1964, the first black president, the first non-southern Democratic president since John F. Kennedy, and likely larger Democratic majorities in Congress than when President Clinton took office in 1993. In a closely divided America, a swing of four votes in a hundred can mean a decisive victory.

Obama's achievement can be explained with a few numbers. The first is 27 percent--President Bush's approval rating in the national exit poll. Pretty dismal. The poll found that voters were split on whether John McCain would continue Bush's policies. But those who thought McCain would be another Bush broke overwhelmingly for Obama, 91 percent to 8. That's a huge, damning margin.

The second number is 93 percent. That's the percentage of voters who gave the economy a negative rating in the exit poll. They supported Obama. And they were right to give the economy a negative rating. The financial crisis is spilling over into the real economy of goods and services. Unemployment is rising and consumption is falling. The week before the election, the Commerce Department announced that consumer spending had dropped 3.1 percent. Consumer spending hadn't fallen since 1991, and this year's decline was the largest since 1980.

The day before the election, the auto companies announced that they had had their worst month in a quarter-century. When economic conditions are as bad as this, of course the party out of power is favored to win an election.

Considering those numbers, the 2008 electoral map isn't all that surprising. Bush, the economy, and Obama's personal and political appeal have pushed the nation toward the blue end of the political spectrum. But, for the most part, the shift is gradual and on the margins. Obama will be president because he took states that Bush won in tight races four years ago. Bush won Ohio by 2 points in 2004. This year Obama won it by 4. Bush won Florida by 5 points in 2004. This year Obama won it by 2.5 points.

Obama's victories in the West were impressive. Bush won Colorado by 5 points in 2004. Obama won it by 7. Bush won New Mexico by 1 point in 2004. Obama won it by a substantial margin--about 15 points. Bush won Nevada by 2 points in 2004. Obama won it by about 13 points.

Virginia has been trending blue since 2001, when Mark Warner was elected governor. In 2004, John Kerry won the Washington suburbs of Arlington, Alexandria, and Fairfax, but still lost the state to Bush, 45 to 54 percent. The next year, another Democrat, Tim Kaine, succeeded Warner. And the year after that, voters replaced incumbent Republican senator George Allen with Democrat Jim Webb in a contest decided by just a few thousand votes. In 2008 Virginia went totally blue. It handed the Democrats as many as three more House seats, replaced retiring Republican senator John Warner with Mark Warner (no relation) by a vote of two-to-one, and swung for Obama by a margin of 5.5 points. Virginia's electoral votes went for a Democrat for the first time since 1964.

The two major surprises on our new map are North Carolina and Indiana. Bush won North Carolina by 12 points in 2004. This year Obama erased that margin and won by a couple tenths of a point. It's the first time since 1976 that North Carolina has voted for a Democratic president. In Indiana the swing toward Obama was even more pronounced. Bush won there by a huge margin of 22 points in 2004. Obama made up all of that ground, eking out a victory of about a point. No Democrat had won Indiana since 1964.

If I were Obama strategist David Axelrod, I'd--well, I'd probably be exhausted right now. But I'd also make sure that President-elect Obama spends the next four years visiting North Carolina, Indiana, Virginia, Ohio, and Florida. He needs to deepen his support in all five states. And I'd also make sure Obama visits Missouri, where at this writing it appears he barely lost; Montana, where he lost by 2.5 points; and Georgia, where he lost by 5.5 points. If Obama holds all the states he won this year and adds those three to his column in 2012, he'll be reelected in a landslide. That's a big "if," of course. The key is a successful first term.

Where does this leave the Republicans? In deep trouble. The GOP is increasingly confined to Appalachia, the South, and the Great Plains. When the next Congress convenes in 2009, there won't be a single House Republican from New England. The GOP is doing only a little better in the mid-Atlantic. There will be only three Republican congressmen in New York's 29-member delegation in the next Congress. Only a third of Pennsylvania's delegation will be Republican--about the same proportion as in New Jersey. There will be a single Republican in Maryland's eight-man delegation. The Rust Belt is hostile territory, too. So are the Mountain West and the Pacific Coast. The GOP is like the central character in Bob Dylan's "Like a Rolling Stone." It's on its own, no direction home.

The Republicans are in demographic trouble. When you look at the ethnic composition of Obama's coalition, you see that it's kind of a mini-America. About two-thirds of Obama's supporters are white and a third minorities. The Republican coalition, by contrast, is white, male, and old. There's the first problem. Overall, Obama may have lost the white vote (while still doing better than Kerry did), but in 2008 whites (not counting Hispanics, per Census convention) made up the smallest proportion of the electorate since the start of exit polling. Obama scored tremendous victories among minorities. He won more than 90 percent of the black vote. He won the Hispanic vote by a two-to-one margin. He won the Asian vote by a similar margin.

Then there are the young. Voters under 30 turned out in only slightly higher numbers than they did in 2004, but they overwhelmingly backed Obama, 68 percent to 30. A successful Obama presidency could lock these voters into the Democratic column for a long, long time.

The most striking divide in 2008 is between rural voters and metropolitan voters. Rural voters back the Republican party overwhelmingly. The problem is that there aren't many of them--and there are fewer all the time. It's the metropolitan voters, the voters who live in cities or suburbs or exurbs, who are growing. And these voters are trending Democratic. Obama won the Philadelphia suburbs, the Washington, D.C., suburbs, the Chicago suburbs in Illinois and Indiana, the Denver suburbs, the suburban counties that make up the Research Triangle in North Carolina, and many more. He won the Orlando suburbs by 20 points. Disney World is Obama country.

Suburbs and exurbs are the most dynamic, fastest-growing places in the country. They are future-oriented. Republicans win when they build out from their rural base and gain support in the exurbs and suburbs. That's how Bush won in 2004. But in Bush's second term, things went awry. The suburban voters abandoned the GOP for the Democrats. The exurbs became volatile battlegrounds. And the GOP was left a minority party.

I think of places like Loudoun County, a northern Virginia exurb. Bush won Loudoun County by 12 points in 2004. In 2008, Obama won Loudoun by 6 points. For the GOP to have a future, it has to reverse that 18-point swing. Otherwise, Republicans better start praying for rain.