After two forums that broke little new ground and produced even less change in the direction of the race, Wednesday night's presidential debate at Hofstra University on Long Island may have been John McCain's last best chance to assert himself in an election that appears to be swinging towards Barack Obama.

McCain came out ready to do just that, challenging his opponent straight away on the effect his tax policies would have on small-business owners such as an Ohio plumber named Joe Wurzelbacher, whom both men evoked the rest of the night as "Joe the Plumber." McCain later expanded his attack into areas he had left off-limits in past debates, including Obama's association with '60s radical William Ayers and the community advocacy group ACORN.

But while the debate saw more political fireworks than either of the candidates' previous two encounters, it also seemed unlikely to give McCain the break he wanted. The format, with both candidates and moderator Bob Schieffer seated together onstage, seemed to play to Obama's strengths, and he appeared more at ease making his points across the table than he had interacting with voters during last week's town-hall-style meeting.

The overall focus on the economy and domestic issues did at least as much to help Obama's performance, and he consistently and confidently delivered his central message: that his policies will help average Americans, while McCain's will continue those of the past eight years. Obama also kept up a strong defense, appearing well prepared to handle Schieffer's questions and well coached to parry McCain's attacks.

When McCain sought to tie Obama to Ayers and ACORN, a group McCain said may be on the verge of "destroying the fabric of democracy" with voter fraud, Obama easily slipped into a brief account disassociating himself from each. Just as readily, he flipped the attack back at McCain, telling him, "I think the fact that this has become such an important part of your campaign, Senator McCain, says more about your campaign than it says about me."

McCain, too, came prepared with his own sound bites, delivering one of the evening's better lines after Obama accused him of supporting the economic policies of the Bush White House. "Senator Obama, I am not President Bush," he said. "If you wanted to run against President Bush, you should have run four years ago." Yet as memorable as McCain's response was, it came late in a race that Obama has already had much success framing as a referendum on Bush.

Throughout the evening, Schieffer encouraged sparring, inviting the candidates to contrast their positions and their records directly. "Why would the country be better off if your running mate became president rather than his running mate?" he asked at one point. While neither Obama nor McCain took the bait there, they did engage in more direct back-and-forth than in previous debates on issues like the economy and the tone of the campaign.

While previous moderators have watched the event slip out of their control as the candidates ran over time and off-topic, Schieffer kept a tighter rein on the proceedings, pushing the candidates with follow-up questions and endeavoring to keep them focused on the topic at hand.

One area where he, like many previous questioners, failed to elicit a straight answer from either candidate was when he asked which programs would have to be cut back or delayed because of budgetary constraints. Obama, as he has in the past, fell back on vague promises to "go through the federal budget line by line" and cut "programs that don't work." McCain's answer, meanwhile, veered from homeownership to energy policy before settling on some familiar points about wasteful spending and ethanol subsidies.

For all the night's political theater, it ended along predictable lines. McCain's closing appeal revolved around comfort and competence, asking voters to decide "whether you can trust us or not to be careful stewards of your tax dollar" and to keep the country safe. Obama repeated familiar lines about "the last eight years," and Democrats and Republicans coming together and investing in the middle class.

That the debate's final notes were in the same key as the overall election does not bode well for McCain, and an instant reaction poll from CNN measured an Obama win. But while politicos will probably have to wait until next week's polls for a clear sense of how the electorate viewed the final presidential debate, at least one focus group last night also recorded a significant victory for Obama.

In a conference call with reporters immediately following the presidential forum, longtime Democratic pollster Stan Greenberg described the reaction he'd just seen among undecided voters in Denver. The debate, he said, had done much to improve such voters' comfort level with Obama, who saw his favorable rating jump after the debate, while McCain's declined.

"The results of this one actually looked more decisive than either of the last two," Greenberg said.