Both campaigns emerged Saturday with evidence of their successes, including competing declarations of victory from various commentators and editorial boards. Obama appeared to have an edge in the various snap polls taken the night of the debate.

Obama's aides asserted that he had passed the threshold test of convincing a huge national audience that he could be commander in chief, and that he had exceeded expectations on delivering his economic message to struggling Americans. McCain's campaign argued that Obama had failed to allay voters' concerns about his qualifications, expressing pride in the frequency with which he had told Obama he did not "understand" various international matters.

The war over shaping the post-debate narrative got off to an exceptionally early start, beginning, in fact, even before the event occurred.

McCain's campaign actually declared victory as early as 10 a.m. Friday morning, hours before the debate began here and even before McCain had agreed to take part in it. The campaign mistakenly released an Internet advertisement to The Wall Street Journal showing McCain proudly looking into the distance. "McCain Wins Debate!" read the type.

A reader of The Washington Post spotted it and alerted the blog The Fix, which promptly posted it before the red-faced McCain campaign removed it.

It was a telling false start to the most important battle to shape perceptions of the election year so far, one pitting two sophisticated war rooms against each another in an all-out effort to harness the increasingly fractured new media. "This is the Super Bowl," said Tucker Bounds, McCain's national spokesman.

Each side had substantive goals for the debate.

For Obama, a 46-year-old Democrat, it was to show he had the stature to serve as commander in chief and, if possible, present himself as the proper steward for the turbulent economy. For McCain, a 72-year-old Republican, it was to move past a topsy-turvy week for both the economy and his campaign and establish his pre-eminence on national security while showing vitality and raising doubts about Obama.

But debates are often won or lost on superficialities. And each campaign was unapologetic in seeking to exploit to maximum effect any gaffe or potentially grating personality ticks of the opponent.

In the era of "live blogging" and real-time fact-checking, YouTube and Twitter, the campaigns began their fight for perceptions minute by minute on Friday night, devising sophisticated plans to tackle the sprawling new media environment unlike any their predecessors employed before them.