SANTA CLARA, Calif. — Senator McCain is vowing to soldier on with his bid for the Republican presidential nomination despite a lackluster fund-raising report and the exodus of much of his campaign’s top staff.

“We’ve fixed the mistakes, and we’re moving on,” Mr. McCain told a lunch for business leaders in Silicon Valley yesterday. “I’m not a good fund-raiser. I will fully admit it. I’m a great — I think I’m an adequate campaigner, excuse my ego.”

Several of Mr. McCain’s senior press aides quit over the weekend after the campaign manager, Terry Nelson, and a longtime adviser to the senator, John Weaver, stepped down. The moves coincided with a financial report showing that the campaign brought in $11.3 million in the second quarter, but spent $13 million. The senator’s bid wound up with $3.2 million on hand, but nearly $1.8 million in debt.

“We structured the campaign in too large a fashion and too bureaucratic a fashion,” Mr. McCain said. “We raised pretty good amounts of money, but we spent too much. It’s not much more complicated than that.”

Mr. McCain told the group that management of the early years of the Iraq war “will go down as a disgrace in the history of this nation.” He said the recent surge in American troops is having some effect at reducing violence but has yet to prompt Iraqi leaders to reach political agreement on key issues. “The bad news is the Iraqi government is not governing effectively,” the senator said. “That is a key and great concern of mine today. … No counterinsurgency ever succeeds unless you can get the political, military, economic, and social progress that all goes together.” Mr. McCain said he saw no merit in a withdrawal plan being offered by two of his Republican colleagues, Senators Warner of Virginia and Lugar of Indiana. “That’s the same strategy we were using, which failed. Train the Iraqis and withdraw. It was failing miserably before, and it will fail again,” he said.

The Arizona senator said a premature withdrawal by America would have horrifying consequences. “Setting a date for withdrawal will mean genocide and catastrophe,” he said. “We are supposed to withdraw to enclaves outside of Baghdad and watch it happen?”

About 100 people turned out to hear Mr. McCain address the business group, the Churchill Club. An organizer said about twice as many people attended a similar event with Mayor Giuliani, who is also seeking the Republican nod and holds a solid lead in California polls.

Mr. McCain described his campaign’s recent travails as entirely the product of its internal structure and his disdain for fund-raising. He glossed over the possibility that some of his financial difficulties and slippage in the polls might stem from his support for the surge in Iraq and his role as champion of the immigration bill that failed to pass the Senate.

“We’re doing fine in the polls, as far as I’m concerned,” the Arizona senator told reporters.

However, some of Mr. McCain’s backers conceded that his views on the war and immigration had dampened his support in recent months. “Clearly, the senator feels strongly on issues that happen to be on the front burner,” a former California secretary of state and Republican Senate candidate who is chairman of Mr. McCain’s campaign in the state, Bill Jones, said. “Those are national security issues and personal security issues that he has spoken about over a long period of time. … That does not mean the main issues he was speaking about today will not have traction with the American people over time.”

Mr. Jones said he was confident about Mr. McCain’s warnings about the dangers of a premature withdrawal from Iraq but could not be sure whether those predictions would be borne out before primary voters begin casting their ballots early next year. While Mr. McCain insisted the campaign shake-up was of little interest to average voters, local news reporters saw the development as an ominous one. “If you can’t run a campaign, how can you r un the country? ” one asked.

Mr. McCain was also asked if the financial troubles and a reported plan to focus on the earliest primary states might lead him to write off California, a state he has promised to vigorously contest. The candidate said he stood by that promise and plans to return to California soon.

The Arizona senator began his talk by talking about the need for action on climate change. “How much time do we have before we act seriously and comprehensively?” he said. Mr. McCain urged greater pressure on China to join the effort, and he insisted that “nuclear power must be part of any equation” aimed at limiting greenhouse gas emissions.

Some in the audience thought the focus on global warming was misplaced, given the dangers posed by the situation in Iraq and the possibility of a nuclear-armed Iran.

“I was surprised he brought that up first,” a bank executive, Alan Jepsen of San Jose, Calif., said. He said the climate issue “will take care of itself” as businesses see the benefit of investing in green technologies.

Mr. Jepsen, a Republican who is undecided in the presidential contest, said he thought the senator’s warnings about a pullout from Iraq were on target, but not likely to resonate with most voters. “The American public doesn’t want to be practical about it,” the banker said. “McCain is saying, ‘I know what will happen. I’ve seen it before.'”