Politics and presidential elections are stories of people, ideas and numbers. On Tuesday night, as much as anything, numbers told a story of how President Obama won a second term despite a climate that had long favored Mitt Romney and the Republicans.

Through much of the year, Romney was running with winds at his back — or, more accurately, with winds in Obama’s face. What Romney could not overcome was the inexorable power of demographic change in a country growing more diverse by the day.

That alone was enough to confound Republican modelers, who either believed or hoped that the electorate would look more like that of 2004 than 2008, both in its racial and political makeup.

But it was not the only story. Obama’s campaign, the most data-driven in the history of American politics, tweaked the electorate in enough places and enough constituencies to eke out victories in virtually every battleground state that had looked competitive on the eve of the election.

Nothing was inevitable about the president’s victory. But against the obstacles in Obama’s path was a belief in Chicago in the glacial power of demographic change. If not exactly a secret weapon, it was an underappreciated asset, and its inexorable quality was seemingly underestimated by Romney’s campaign and by many Republican strategists.

Obama advisers were certain that the electorate would have fewer white voters than it had in 2008, just as it had fewer in 2008 than in 2004 and in elections before that. Since 1992, the share of the white vote has fallen from 87 percent to 83 percent to 81 percent to 77 percent and then to 74 percent in 2008.

On Tuesday, according to exit polls, whites accounted for 72 percent. Obama received 39 percent of that white vote, compared with 43 percent in 2008. That compares with the 42 percent Al Gore captured in 2000 and the 41 percent John F. Kerry took in 2004. In fact, it is the lowest for any Democrat running in a two-way contest since 1984, when Walter Mondale received 35 percent of the white vote.

Obama offset his weak performance among white voters by winning 80 percent of the non-white electorate. He captured 93 percent of the African American vote, 71 percent of the Hispanic vote (up from 67 percent four years ago) and 73 percent of the Asian vote (up from 62 percent in 2008).

Obama also won 80 percent of the non-white vote four years ago, which was a shade under Jimmy Carter’s 82 percent in 1976, the highest share for any Democrat in the past 40 years. At the time, however, non-whites made up just 10 percent of the electorate, and African Americans accounted for by far the largest share.

Obama’s campaign, though, did not rely solely on the power of demographic change. It set out to maximize it as much as possible. For the past 18 months, the team invested in what it called Operation Vote, which was aimed exclusively at the key constituencies that make up Obama’s coalition: African Americans, Hispanics, young voters and women (particularly those with college degrees.)

The decision to set up a parallel organizing team, to supplement traditional mobilizing efforts that were geographically based, was one of the upshots of the shellacking Obama and the Democrats received in the 2010 midterm elections. Research showed the Obama camp that voters are connected not only by geographically but also by what one senior official called “common concerns” of their natural constituencies.

Once they were identified, the campaign communicated with them as directly as possible. For example, it targeted places where these constituencies gathered and quietly bought advertising in niche markets that appealed to them. The operation also worked harder to recruit volunteers for get-out-the-vote efforts. In 2008, it often relied on younger volunteers from other states.

The result was that, in Ohio, the share of the African American vote jumped from 11 percent to 15 percent and Obama won 96 percent of the demographic’s votes. In Florida, the Hispanic share of the vote grew from 14 percent to 17 percent, and Obama increased his percentage from 57 to 60, doing well in Cuban American and non-Cuban Hispanic precincts.

The campaign can’t claim all the credit for the increases in the African American or Latino share of the vote in some of these states. But it was attentive to the constituencies needed to win and the places it had to capture.

There was talk before the election that young voters were not as energized as they were four years ago. But the share of the vote accounted for by those age 18 to 29 rose from 18 percent to 19 percent. Nationally, Obama received a lower percentage of those young voters this time, however, falling from 66 percent to 60 percent. But in Florida, he increased his share from 61 percent to 66 percent.

In other states, Obama slipped among young voters, but the campaign hardly ignored them. The president campaigned repeatedly at colleges during the fall and spent what an official called “huge” resources on local organizing.

Because many votes are yet to be counted, it’s not clear whether overall turnout nationally will be as high as it was in 2008. But the largest declines may be in states that were not considered battlegrounds and that did not receive the attention and resources from either campaign that the contested states got. The Obama campaign said that unofficial numbers show turnout in four of the battlegrounds — Iowa, Nevada, North Carolina and Wisconsin — was higher than it was four years ago.

The coalition Obama assembled in 2008 is unique, doing better among minorities and college-educated voters than other Democrats have done. Democrats must ask whether it will outlast his presidency. On Tuesday, that coalition was reassembled and proved just big enough, in enough states, to give him a narrow victory in the popular vote and a far more comfortable win in the Electoral College.

For previous columns by Dan Balz,
go to postpolitics.com.