WASHINGTON — Senator McCain sought to minimize damage to his man-of-character image and his presidential hopes yesterday, vigorously denying and denouncing a newspaper report suggesting an improper relationship with a female lobbyist.

“It’s not true,” the likely Republican nominee said of the report that implied a romantic link with telecommunications lobbyist Vicki Iseman and suggested Mr. McCain pushed legislation that would have benefited her clients. “At no time have I ever done anything that would betray the public trust,” he said. Mr. McCain, who is a four-term Arizona senator and a veteran of the Vietnam War, described the lobbyist as a friend.

Mr. McCain and his wife, standing together at a news conference, said they were disappointed that the New York Times ran its page one article, and his campaign referred to a “smear campaign” and “gutter politics” in the midst of the presidential race.

The allegations in the Thursday report in the Times — and a story in the Washington Post — contradict core themes of Mr. McCain’s campaign — that he would bring honor and integrity to the White House as well as a record of changing business-as-usual Washington ways.

Even the suggestion of marital impropriety — though rejected by both Mr. McCain and his wife — would seem to risk further damaging his acrimonious relationship with the social conservatives whose support he desperately needs in the general election campaign against a fired-up Democratic Party.

In a twist, however, there were early signs that the brouhaha might actually help Mr. McCain solidify the GOP base.

Conservative pundits who are some of Mr. McCain’s harshest critics could have jumped on the issue to question the strength of Mr. McCain’s family values. Instead, they went after the Times. “There is nothing in it here that you can say is true,” Rush Limbaugh told his radio listeners. He accused the newspaper of “trying to take him out.” Another conservative voice, Laura Ingraham, contended the newspaper was trying to “contaminate” the GOP’s nominee with an “absurd attack.” By yesterday afternoon, the Arizona senator had begun a fundraising appeal based on the story. “The New York Times … has shown once again that it cannot exercise good journalistic judgment when it comes to dealing with a conservative Republican,” campaign manager Rick Davis wrote in an e-mail to supporters. “We need your help to counteract the liberal establishment and fight back against the New York Times by making an immediate contribution today.”

“We think the story speaks for itself,” Times Executive Editor Bill Keller said in a written statement. “On the timing, our policy is we publish stories when they are ready.”

At the very least, the episode gives Democrats an opening to try to exploit Mr. McCain’s decades-long ties to Washington even though he’s known as a Republican lawmaker willing to stand up to special interests and reduce the influence of lobbyists.