"We're focusing on the economy," the Arizona senator said in an interview aired Tuesday on "The Early Show" on CBS. "Listen to me. I'm the candidate, and this campaign is about the economy."
Polls show that voters have more confidence in Obama when it comes to economic issues. McCain has been using a remark by Obama that he wanted to "spread the wealth around" to criticize the Democrat as favoring socialist economic policies.
Democratic vice presidential candidate Joe Biden provided McCain an opening on a different issue - readiness to be president - when he told supporters at a weekend fundraiser: "Watch, we're gonna have an international crisis, a generated crisis, to test the mettle of this guy."
"We don't want a president who invites testing from the world at a time when our economy is in crisis and Americans are already fighting in two wars," McCain told a crowd Monday in Belton, Mo.
"What is more troubling is that Sen. Biden told their campaign donors that when that crisis hits, they would have to stand with them, because it wouldn't be apparent Sen. Obama would have the right response," added the Republican nominee, who was spending Tuesday in Pennsylvania, another battleground.
"Forget apparent," McCain said. "Sen. Obama won't have the right response, and we know that because we've seen the wrong response from him over and over during this campaign."
Biden, however, drew a far different conclusion than McCain. He compared Obama to President John Kennedy and said, "They're going to find out this guy's got steel in his spine."
McCain went on the criticize Obama's opposition to President Bush's decision to send tens of thousands of additional U.S. troops to Iraq, as well as his rival's more restrained response to Russia's invasion of Georgia this summer.
Obama gained a forceful rebuttal to those concerns over the weekend, when former Secretary of State Colin Powell, a retired four-star general and former chairman of the Joint Chiefs of Staff, endorsed Obama and attested to his readiness to be president.
Powell also criticized McCain's selection of Alaska Gov. Sarah Palin as his running mate, saying she failed to meet the primary qualification for a vice president: the ability to assume the presidency at any time.
The attacks on Obama come two weeks before Election Day, and as Obama maintains a lead in national polling as well as in surveys conducted in key battleground states.
It was unclear whether McCain might step back from his attacks after Obama's campaign announced that he will suspend campaigning for two days later this week to visit his gravely ill 85-year-old grandmother in Hawaii.
Amid concern that battleground states were slipping from their grasp, McCain aides scheduled a daylong tour across Pennsylvania on Tuesday.
McCain scheduled rallies in Bensalem, near Philadelphia; Harrisburg; and Moon Township, outside Pittsburgh.
