"No new taxes," the likely GOP presidential nominee said during a taped interview broadcast Sunday.
McCain told ABC's "This Week" that under no circumstances would he increase taxes, and added that he could "see an argument, if our economy continues to deteriorate, for lower interest rates, lower tax rates, and certainly decreasing corporate tax rates," as well as giving people the ability to write off depreciation and eliminating the alternative minimum tax.
McCain was defending his support for an extension of tax cuts sought by President Bush, which McCain voted against. The Arizona senator now says allowing the tax breaks to expire would amount to an unacceptable tax increase.
Later Sunday, the Democratic Party criticized John McCain's statements on continuing the tax cuts, saying his policies would not differ from the past eight years under the Bush administration.
"John McCain showed today that he is about as far from a maverick as they come," said Karen Finney, spokeswoman for the Democratic National Committee.
McCain's "no new taxes" statement marked a turnaround. Last September, he was forced to defend his refusal to sign a no-new tax pledge offered by the conservative Americans for Tax Reform.
"I stand on my record," he said during a televised debate in Durham, N.H. "I don't have to sign pledges."
The leading contender for his party's presidential nomination, McCain blamed out-of-control spending for a lack of enthusiasm among Republican voters.
"Spending restraint is why our base is not energized," he said. "I think it's very important that we send a signal to the American people we're going to stop the earmark pork-barrel spending."
McCain said the $35 billion worth of spending on special projects that Bush signed into law in the last two years amounts to a $1,000 tax credit for every child in America, and would have been better for the economy if spent that way.
McCain also said he was open to the idea of helping homeowners facing foreclosure, provided they were "legitimate borrowers" and not "engaged in speculation."