(CNN) -- Sen. John McCain played offense against Sen. Barack Obama during much of the final presidential debate as he challenged his rival on his policies, judgment and character.



Obama said he is the candidate who can bring "fundamental change" to the country and continued to try to link McCain to President Bush.



In one of the more forceful moments of the debate, McCain turned to Obama and said, "I am not President Bush."



"If you want to run against President Bush, you should have run four years ago. I'm going to give a new direction to this economy and this country," the Arizona senator said.  Watch McCain say he's no Bush »



McCain aides said they had been working on him to be more explicit in drawing a distinction between himself and Bush.



With less than three weeks before the election, it was one of several jabs McCain took at his opponent, who is leading the race in most national polls and has an 8-point lead in CNN's average of national polls.



A CNN/Opinion Research poll of people who watched the debate found 58 percent said Obama did the best job while 31 percent said McCain did. Watch entire debate:  Part 1 » |  Part 2 » |  Part 3 »



The poll has a margin of error of plus or minus 4 percentage points, and the sample of debate-watchers in the poll were 40 percent Democratic and 30 percent Republican.



McCain touted what he called his "long record of reform" and said to Obama: "You have to tell me one time when you have stood up with the leaders of your party on one single major issue."



Obama said he has a "history of reaching across the aisle" and pointed to his support for charter schools, pay for performance for teachers and clean coal technology.  See scenes from the debate »



"Sen. Obama, your argument for standing up to the leadership of your party isn't very convincing," McCain said.



The third and final presidential debate took place at Hofstra University in Hempstead, New York, and was moderated by Bob Schieffer of CBS News.  Analysts weigh in on the debate »



As McCain tried to put the pressure on Obama, he told the Illinois senator that voters need to "know the full extent" of his relationship with Bill Ayers, a former 1960s radical who belonged to the Weather Underground.



"Mr. Ayers is not involved in this campaign, he has never been involved in my campaign, and he will not advise me in the White House," Obama said.



McCain's campaign has charged that Obama's association with Ayers should cause voters to question his judgment.



Ayers was a founding member of the radical Weather Underground, a group that was involved in bombings in the early 1970s, including attacks on the Pentagon and the Capitol.



Obama said Ayers had committed "despicable acts" 40 years ago, but pointed out that he himself had been 8 years old at the time.  Watch what Obama says about Ayers »



Obama said Ayers has become the "centerpiece" of McCain's campaign and said the fact that McCain keeps bringing Ayers up "says more about your campaign than it says about me."



The Republican nominee also brought up comments made last weekend by Rep. John Lewis and pushed Obama to repudiate them.



Lewis on Saturday compared the feeling at recent GOP rallies to those of segregationist George Wallace.



"I think Congressman Lewis' point was that we have to be careful about how we deal with our supporters," Obama said.



"I do think that he inappropriately drew a comparison between what was happening there and what had happened during the civil rights movement, and we immediately put out a statement saying that we don't think that comparison is appropriate," he said.



As the candidates butted heads over tax policy, both made frequent mention of "Joe the plumber."  Watch voters react when 'Joe' comes up »



Last weekend, while Obama was canvassing for support in Holland, Ohio, the
which candidate did more viewers think won the debate? What person did McCain and Obama mention a lot? Who started the debate of economic plans? Viewers say who won the debate?
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question: which candidate did more viewers think won the debate?, answer: Obama | question: What person did McCain and Obama mention a lot?, answer: Bush. | question: Who started the debate of economic plans?, answer: Barack Obama | question: Viewers say who won the debate?, answer: Obama