McCain, Obama begin final sprint after last debate Opinion polls show more voters say they trust Obama's leadership on the economy, which has dominated the campaign-trail discussion and dwarfed McCain's expertise in foreign and military policy. The two candidates will be on the same stage again on Thursday night when they give speeches to the Al Smith dinner, a New York political tradition and regular stop for presidential candidates. Before the dinner, McCain will make a quick campaign trip to Philadelphia and Obama will visit New Hampshire. During the debate, McCain called on Obama to explain his relationship with 1960s radical William Ayers, who served with Obama on a community board in Chicago and hosted a political event for him early in his career. Obama distanced himself from Ayers. "Mr. Ayers is not involved in my campaign. He has never been involved in this campaign. And he will not advise me in the White House," Obama said. 'PRETTY TOUGH' Both candidates admitted the campaign's tone was "tough" and blamed the other. McCain said Obama had spent more money on negative ads than any candidate in history, while Obama noted a recent study said 100 percent of McCain's ads had been negative. "It's gotten pretty tough, and I regret some of the negative aspects of both campaigns. But the fact is that it has taken many turns which I think are unacceptable," McCain said. He demanded Obama renounce the comments of Georgia Rep. John Lewis, a leader in the U.S. civil rights movement, who recently linked McCain to 1960s segregationist leader George Wallace.