(Chip Somodevilla / AP)

If tonight's presidential face-off between Barack Obama and John McCain were held before, say, the Princeton University Debating Society, it might have been scored a tie. On points, the two contenders were evenly matched. Both spoke clearly, crisply and confidently about the major issues facing the country, rebutting his rival's attacks and launching his own assaults when necessary. Neither looked at his watch, or sighed, or forgot to remove his 5 o'clock shadow. There were no memorable gaffes--or devastating zingers--that will define the debate on cable news and, later, in the single sentence devoted to the event in our grandkids' high-school history textbooks. It was a consummately professional affair.

But alas: presidential debates aren't scored scientifically. Committed partisans may keep track of everything their guy got right. But undecided swing voters--the ones who will decide the election--don't tally up points. Instead, they link what happens on stage--in a broad, impressionistic sense--to the narratives they'd already heard about the candidates. Which means it's up to the two men performing at the podiums to reinforce the positive, preexisting story lines and disprove the negative ones. In the end, Obama supporters will say Obama won. McCain supporters will say McCain won. The question is who won over more undecideds.

Tonight, I think John McCain was the more effective combatant.

There are two reasons why. The first is that he constantly--obsessively, really--spiked his responses with small but pointed jabs at Obama that unfailingly related to subjects he (McCain) wanted to talk about, whatever the original topic of discussion. This tactic had a dual effect. First, Obama couldn't help but take the bait; he must've said "that's not true," "let me correct the record" or "I just have to respond" a dozen times over the course of the evening. Second, Obama's defensiveness immediately shifted the conversation to McCain's home turf--where it remained, often for minutes at a time.

McCain's strategy was on display from the start. Fielding a question on the current fiscal crisis--not his best area--the senator delivered a flabby, unconvincing answer. But he swiftly segued to a criticism of earmarks and "out of control spending" in Washington--a pet issue that resonates as "reform" among voters--and slammed Obama for requesting $932 million for Illinois since arriving in the Senate (a stat he repeated three or four times). Of course, earmarks only represent $18 billion in spending--a tiny sum, as Obama pointed out. But the Democrat was still forced to rebut McCain's attack. Similarly, McCain deftly transformed a question about how the Wall Street bailout would affect the next president's priorities into an assault on Obama's tax plan and hefty spending proposals, both issues that (again) tend to favor the Republican. As a result, most of the economic portion of the debate--a half-hour or so that should've played to Obama's strengths--was spent on McCain's poll-tested terrain (earmarks, spending and tax cuts) instead of Obama's (the current economic crisis). McCain pulled the same trick on foreign policy, focusing the conversation on Obama's opposition to the surge and willingness to meet with unfriendly foreign leaders. Much of what the Illinois senator said on these subjects was smart. It's just that he was reduced to an essentially reactive posture, either defending himself or agreeing with McCain's more assertive remarks over and over again. (Obama muttered the phrases "John's right" or "I agree" about a dozen times tonight; the GOP quickly cut a Web ad.) Simply put, McCain was in control.

The second thing McCain had going for him was a sort of optimism. You'd think from the previous paragraph that the Arizonan was all negativity. But that wasn't the case. Obama wanted--understandably so--to tie McCain to the catastrophes of the last eight years; McCain wanted to pretend they'd never happened. Ironically enough, this turned out to be a rhetorical advantage for the Republican. Time and again, Obama would move to lay blame for a past failure--and McCain would pivot to a better future. On the economy, Obama looked back at a "failed policy" of "shred[ding] regulations and consumer protections"; McCain looked ahead to the spending he'd cut and the people he'd hold accountable as president. On Iraq, Obama focused on how we got in; McCain focused on how we'll get out. I'm not saying Obama was wrong on the issues. His criticism of the Bush Administration's incompetence was cogent, clear and largely correct. Nor am I suggesting that McCain didn't delve into the past; he was clearly at pains to list the places he's visited and the leaders he's known. What I am arguing is that while Obama blasted Bush, McCain looked past him. Coupled with his reliance on catchy anecdotes over bullet-pointed policy positions--"defying Reagan on the Lebanon deployment, the bracelet belonging to the mother of a dead soldier, the firing of Chris Cox, the bear DNA"--this post-Bush perspective may help McCain appeal to moderates, a group that's more interested in solving problems than engaging in the partisan blame game. It was probably a matter of necessity more than anything else. But he used it to his advantage.

*The National Journal's Ron Brownstein sums it up nicely: "The fundamental tug of war in this election is the competition between Obama and McCain to frame the choice in the minds of swing voters. McCain wants them to view their choice largely in personal terms--to ask themselves: which of these two men has the experience, background and instincts I want in a president? Obama wants voters to view the choice less in personal than generic terms--he wants voters to ask which of these two men offers a direction for the country that I support. McCain Friday night was more successful than Obama at steering the discussion back to the terrain that favored him."*

McCain wasn't perfect tonight. Far from it, in fact. He scowled, smirked and refused to look at his rival, conveying an air of condescension that could turn off some undecideds. He twisted the facts in a few of his responses, including the ones on the Eisenhower letters and his Lebanon vote. He compared Obama to Bush, which is laughable. (Obama laughed.) And he seemed overeager to say that his opponent didn't "understand" the issues--despite ample evidence to the contrary.

For his part, Obama was hardly a dud. He proved himself as a sensible, studious, informed thinker--certainly a contrast to the "naive celebrity" caricature that McCain and Co. have tried to peddle to the populace. He had the best soundbite of the night. "You said it was going to be quick and easy," Obama said. "You said we knew where the weapons of mass destruction were. You were wrong. You said that we were going to be greeted as liberators. You were wrong. You said that there was no history of violence between Shiite and Sunni. And you were wrong." (Most Americans would agree.) Obama was even "presidential"--which was the only bar he really had to clear.

But ultimately I suspect that McCain did more to reinforce his message--I'm a tough leader who will cut waste and get Iraq right--than his opponent. Repetition may bore political junkies, but it helps candidates connect with casual voters--as do memorable (if corny) anecdotes. Obama relied instead on abstractions and stats. What's more, McCain outperformed low expectations set by a week of somewhat erratic behavior, including his impetuous and ineffective campaign suspension. Whether that makes any electoral difference remains to be seen. The contours of the race and the climate in the country still favor Obama, who holds a small but consistent lead in recent polls. To remake the landscape, McCain would've had to score a knockout blow. He didn't come close. The question, then, is whether he can keep delivering such solid performances from now until Nov. 4--and whether even that will be enough.

UPDATE, 12:45 p.m.: An interesting observation from the Politico's Ben Smith:

The mild consensus in the press file was that McCain won, if not in particularly dramatic fashion. The two insta-polls out -- from CBS and CNN -- found the opposite: That Obama won by a wide margin. CBS had it 39% to 25% for Obama, CNN 51% to 38%. Maybe the difference was expectations. People covering the campaigns think of Obama as a much-improved debater, and McCain as at times a weak one. McCain, by that standard, overperformed. But people tuning into the race now now think of McCain as an experienced hand, and Obama as a newcomer. Obama more than held his own, and McCain failed to expose him -- as he tried -- as out of his depth.

Damn liberal media, always out to ge--oh, wait. Never mind.

Seriously, though--it's worth remembering that reaction to a presidential debate can take awhile to crystallize, and it has as much to do with the narrative that emerges in the MSM as what actually happened on stage. My take reflects what I saw in the hall. But by Monday morning McCain's "condescension"--or some other sticky moment--may be the only thing anyone remembers. Let Spin Wars begin.

UPDATE, Sept. 27: According to the nonpartisan researchers at Factcheck.org (a NEWSWEEK partner), "McCain and Obama contradicted each other repeatedly during their first debate, and each volunteered some factual misstatements as well." For a tally of their untruths, click here.

*Updated Sept. 27