Although Mr. McCain’s problems have been apparent for months — he shook up his staff and promised to run a leaner operation after a disappointing fund-raising performance in the first quarter — aides said the full scale of his difficulties only became clear to him toward the end of last month. Donations were drying up, in part because of Republican opposition to Mr. McCain’s stances on issues like immigration, and the campaign was falling far short of its fund-raising goals.  And the campaign had burned through most of the $24 million it had raised in the first half of the year on hefty salaries for staff members and consultants, a heavy travel schedule and all manner of other expenses, leaving it with less cash at the end of June than even the bare-bones presidential campaign of Representative Ron Paul, Republican of Texas.  Aides said that the problems started to peak two weeks ago at a meeting with Mr. McCain and about 100 contributors in 100-degree weather at his home in Sedona, Ariz. It was just before that meeting, aides said, that Mr. McCain and his wife, Cindy, were told how bleak the campaign’s financial situation was.  They said the McCains were startled and enraged.  Aides said Mr. McCain expressed concern that the image of his campaign overspending would invite mockery from opponents at a time when he is attacking excessive government spending. One McCain associate said the senator expressed astonishment at the Sedona meeting that he had spent so much money without putting a single advertisement on television.  It was that gathering that led to the shakeup announced on Tuesday.  Mr. McCain’s campaign quickly moved to plug the holes caused by the departures of Mr. Weaver and Mr. Nelson. It announced that Rick Davis, who was serving as the chief executive officer in the campaign, would step in as manager, reprising the role he fulfilled for Mr. McCain in his 2000 presidential bid. Mr. Davis had battled furiously with Mr. Nelson and Mr. Weaver for influence over the past three months, aides said.  “No, no, no, no,” Mr. McCain said when asked by reporters on Capitol Hll if his campaign was in trouble. “I’d describe the campaign as going well. I’m very happy with it.”  When asked whether he intended to stay in the presidential race, he replied, “Of course.”  But Mr. McCain finds himself in a situation that his own supporters said Tuesday was largely a function of what has been his uneven performance as a candidate and in overseeing his campaign.  They said Mr. McCain and his aides had made two fundamental strategic decisions that so far have proven flawed. One was that voters would reward Mr. McCain for taking principled decisions on issues — especially immigration, where he is out of step with much of the grass roots of the Republican Party, and the war in Iraq, where his steadfast support for fighting on has left him on the defensive. Instead, polls suggest that Mr. McCain has alienated much of the Republican base.  The other stemmed from a belief in Mr. McCain’s inner circle last year that he would be anointed the Republican front-runner and would enjoy the political and financial advantages that go with it.  Last November, Mr. Davis, with the assent of Mr. Nelson and Mr. Weaver, argued that Mr. McCain would have no trouble supporting a political machine on the scale of the 2004 Bush campaign, presenting himself as the president’s anointed heir.  From that perspective, Mr. Davis argued, the campaign should expect to raise $120 million this year, including $50 million in the first six months, about twice as much as what turned out to be true.  “We had false assumptions about how much money could be raised,” said Mark Salter, a senior aide to Mr. McCain. “It’s not fair to pin it on anybody. We all had this expectation that money was going to be very easy for us to raise.”  Beyond that, Mr. McCain muddied up his image as a moderate independent in his second bid for his party’s nomination. He embraced President Bush after their bitter fight in 2000, and sought to make amends with the religious conservative leaders after denouncing them. But by all appearances, he has not had great success in fortifying his stand with the party’s conservative wing, even as he may have undercut his appeal as an independent candidate.  Mr. Nelson told Mr. McCain he was quitting Tuesday morning, after offering his resignation several times since the campaign’s announcement last week that its fund-raising had been weak for the second quarter in a row, campaign officials said. Mr. McCain’s advisers pointedly said he made no effort to dissuade Mr. Nelson.  Mr. Weaver quit after learning that Mr. Nelson, who was the political director of Mr. Bush’s re-election campaign in 2004, was leaving and that Mr. Davis — with whom Mr. Weaver has feuded for years — was stepping in. Aides said some lower-level aides, most of whom Mr. Nelson had brought over from the Bush campaign, quit as well. Mr. Weaver’s move was unexpected even by him; he gave up a rent-controlled apartment in Greenwich Village three weeks ago to move to Washington.  Mr. McCain, after first insisting neither man had been fired, described the departures as “a consensus decision.”  They came a week after campaign aides said they were laying off 80 members of its 120-member staff. Mr. McCain’s advisers were trading blame throughout the day about what was at fault — lackluster fund-raisers overseen by Mr. Davis or exuberant spending under the purview of Mr. Nelson.  McCain aides said a third close friend and adviser, Mr. Salter, was now taking a relatively diminished, though still important, role in the campaign, serving as an unpaid senior adviser. Mr. Salter is perhaps Mr. McCain’s closest staff member; they have co-written several books and Mr. Salter will travel with Mr. McCain to New Hampshire on Friday.  The campaign’s financial expectations could be seen in its spending reports. In the first three months of the year, it paid $30,000 to Mr. Davis’s firm, Davis Manafort; $42,600 to Mr. Nelson as well as $10,000 to his firm, Dawson McCarthy Nelson Media; and $71,000 to Mr. Weaver. It also paid Michael Dennehy, the campaign’s former political director, $52,000, plus $15,000 to the Dennehy Group and $13,000 for Mr. Dennehy’s travel.  The campaign paid rent not only in Iowa, New Hampshire and South Carolina, but also in states where most candidates do not bother at this stage, like Alabama and Michigan, its first quarter filings showed. Beyond that, the campaign spent $11,000 for photography, $27,000 for a parking lot operator in Washington, $24,723 to Carey International for limousines and $460,000 to Flight Options for charter planes.  There were also reports of Mr. McCain’s aides benefiting by their association with the campaign, exacerbating long-standing tensions between Mr. Weaver and Mr. Davis. The campaign retained a company co-owned by Mr. Davis, 3eDC, to run its Web site, and Mr. Weaver went to Mr. Davis and tried to stop the arrangement, aides said. The campaign owed the company $175,802 at the end of the first quarter, according to its filings.  Mr. Weaver’s fiancée, Angela Hession, was a strategist for Mr. McCain; at one point she was being paid $1,000 a month, but — like many other advisers since the financial problems overtook the campaign — began working without pay. She was among the staff members who left on Tuesday.  Jim Rutenberg, Jeff Zeleny and Michael Cooper contributed reporting.  A version of this article appears in print on , on Page A1 of the New York edition with the headline: McCain Campaign Drops Top Aides; New Doubts Rise. Order Reprints| Today's Paper|Subscribe
The departure left Senator John McCain’s campaign team gutted and raised new doubts about his ability to continue in the race.