McCain did not vote on the measure when it cleared Congress on Saturday, although he returned to Washington after Friday night's campaign debate in Mississippi. McCain said he was working on other matters at the time of the vote, including negotiations on a bailout of the financial industry.
"I certainly would have done everything in my power to remove those earmarks," he told ABC's "This Week" in an interview. "But I may have voted for it if, I probably would have ended up voting for it, but I decry a system where individual members are, are faced with taking all this unacceptable, outrageous stuff that has contributed to the largest growth in spending since the Great Society."
By one estimate, the bill includes 2,322 pet projects sought by lawmakers for their home districts and states, totaling $6.6 billion.
The measure is needed to keep the government running after the new budget year begins Wednesday. The same bill also lifted a long-term ban on offshore oil drilling and included billions of dollars to subsidize loans to the battered auto industry.
McCain reversed course earlier this year to announce support for additional drilling to help reduce U.S. dependence on foreign oil. The auto industry loans, designed to help car makers retool their factories to produce more efficient models, are particularly important in swing states such as Michigan and Ohio.
McCain said he intends to resume campaigning full-time on Monday, after a week in which he announced he was suspending all such activity to return to Washington and become involved in negotiations on the financial industry bailout.
Polls suggest the race now slightly tilts Obama's way, with the fading of the gains McCain made with his Republican National Convention this month and the emergence of the economic crisis as the dominant issue.
But more than five weeks remain in a campaign that already has undergone innumerable swings in momentum. The calendar includes three more nationally televised debates, including one scheduled for Thursday between vice presidential running mates Sarah Palin, the Republican governor of Alaska, and Joe Biden, a Democratic senator from Delaware.
McCain said he hopes to be able to support a newly negotiated $700 billion deal to help the financial industry, but said he wants to see the details first. "This is something that all of us will swallow hard and go forward with," he said.
His decision to return to Washington to insert himself in the negotiations between the Bush administration and Congress drew strong criticism from Democrats, who said his presence hurt rather than helped. He defended his decision strongly.
"I'm a Teddy Roosevelt Republican. I've got to get in the arena when America needs it," McCain said. "And if that judgment wants to be made that I, whether I helped or hurt, I'll be glad to accept the judgment of history."
On other issues, McCain:
-Appeared to concede that his health care plan would result in higher taxes for some. McCain favors a $5,000 annual tax credit to help individuals and families afford health insurance, but that could leader employers to drop their current plans, including some that could not be replaced for $5,000.
"It depends on, on, on what plan they have," McCain said. "But that's usually the wealthiest people. Ordinary working Americans have the kind of, or an overwhelming majority have the health insurance plans that this tax credit, refundable tax credit, will actually put more money in their pockets for the purchase of health care than what they had before."
-Defended Palin from increasing criticism, including from some conservatives, that she is ill-prepared to become first in line of succession to the presidency.
"They can complain all they want to," he said. "...I'm so happy that she is part of the team. And she's brought a kind of exuberance and a kind of excitement that makes you really think that political campaigns again can still be something that is an exciting trip."