Right now, Barack Obama is favored over John McCain in the race to secure the 270 electoral votes required to claim the White House. But when you listen to the tough-talking senior aides running his campaign, you realize that Mr. Obama wants something more than just a victory. That could be his undoing.George W. Bush won the White House with 271 electoral votes in 2000 and 286 in 2004, barely exceeding the total needed. Today, most national polls suggest that the 2008 race is very tight. Yet Mr. Obama seems to be targeting enough states to net a total closer to 370 electoral votes.

His potential to change the makeup of the electorate – especially to bring more young and minority voters into the mix – may offer a new formula for victory. And his financial advantage enables him to spread resources in more than a half-dozen previously solid red states.

There are three rationales that support thinking big.

•First, spending time and money in red states puts the Republicans on the defensive, forcing John McCain to use precious resources to keep states firmly in his column.

•The more states Mr. Obama can put in play as potential wins, the more combinations that are available to him to reach 270 electoral votes.

•Should he win by a large margin, Mr. Obama would have a potent mandate to unite the country and bring about the fundamental changes in Washington he claims to seek.

But if the strategy backfires, it could cost Mr. Obama a race he should win. As national polling has shown a closer race, the good news for Mr. Obama is that almost all of the solidly blue states won by Al Gore and John Kerry are still safely in his column – anchored by New England, New York, the Mid-Atlantic states and the West Coast.

But that coalition does not get the Democrat to 270 electoral votes. And the bad news is that Mr. McCain is consolidating his support in some of the red states that Mr. Obama hopes to challenge, including much of the South, the Plains and the Great Basin states.

Which means the most vital targets for Mr. Obama are much the same as they were for his party in 2000 and 2004: Pennsylvania, Florida, Michigan, Ohio, Wisconsin, Iowa, Nevada and a handful of smaller states. Analysts believe that the two red states in which Mr. Obama has the best chance – Virginia and Colorado – will be tough for him to win. And the other red states on his wish list – Alaska, North Dakota, Indiana, Georgia, Montana and North Carolina – will be even harder.

Trying to reach a wider swath of voters in a multimedia, transient world is more challenging than ever and requires not just plenty of money but an enormous allocation of the candidate's time – the single most valuable asset of any presidential campaign.

Mr. Obama's campaign team envisions taking the grass-roots methods and enthusiasm that helped win caucuses and primaries against Hillary Clinton and applying them to the broader canvas of a general election. But it will take far more votes to beat Mr. McCain, and the kind of voters who showed up for Mr. Obama in most primary and caucus states are more liberal and partisan than the centrist and independent citizens who will decide this election in the battleground states.

If Mr. McCain pulls off a victory in November, there will be a lot of postmortem scrutiny about the prudence of playing it safe vs. the dream of shooting the moon.

Mark Halperin is an editor at large and senior political analyst for Time magazine and editor of The Page at time.com.