The woman, wearing a union T-shirt, said she was making $17,000 a year and cannot afford housing, gas, food or health care for her children. "We cannot continue this way," she said.

McCain said the point of his education platform was to boost pay for "a great and outstanding teacher like you" and other educators who are passionate about their work.

"I want to reward good teachers," said McCain.

Members of the audience said afterward they were glad to have heard from McCain, even if it didn't change their minds.

"Winning votes, I'm not so sure, but friends, yes," the Rev. Ronald Terry, pastor of New Friendship Baptist Church in Macon, Ga., said of McCain's appearance.

Marjory Shields, a Penn State extension nutritionist from Croydon, Pa., said McCain said nothing to make her waver from her support of Obama.

"I gave him the courtesy of listening to his platform. I thought that in order for me to make an informed vote this November I really need to hear what all the candidates have to say," Shields said.

"As far as my opinion on his speech, I feel he did not address certain key issues I wish he would have elaborated on," such as more specifics on education funding, she said.

McCain said vouchers and merit pay for teachers whose students perform well are two important ways to help kids in failing schools.

"After decades of hearing the same big promises from the public education establishment, and seeing the same poor results, it is surely time to shake off old ways and to demand new reforms," he said. "That isn't just my opinion. It is the conviction of parents in poor neighborhoods across this nation who want better lives for their children."

Both the merit pay and voucher proposals have met stiff opposition from teachers unions. Obama has indicated he would support some kind of merit pay system for teachers, if teachers help craft it.

Later Wednesday, McCain traveled to Omaha, Neb., where he toured Werner Enterprises, a trucking company, and again promoted his plan for a summer suspension of the federal gas tax to help drivers cope with surging fuel prices.

Werner executives said that a yearlong gas tax holiday would save them approximately $40 million, which could be spent on making their trucks more efficient.

Asked what individual Americans could do to lower the price of gas, McCain said they "can practice conservation" and pressure Congress to allow more offshore drilling for oil.

Meanwhile, Obama warned Wednesday about the danger of "fighting the last war" as he pledged to focus on emerging nuclear, biological and cyber threats if elected president.

Among those joining him for a panel discuss at Purdue University in West Lafayette, Ind., were two potential running mates, Sen. Evan Bayh, D-Ind., and former Sen. Sam Nunn, D-Ga. As the former governor of a Republican state, Bayh could help Obama. Nunn, a defense expert from the South, would burnish the ticket's experience.

When asked if he were interested in the job or had provided material to vetters, Bayh repeatedly referred reporters to the Obama campaign. Nunn said he thought an Obama-Nunn ticket was unlikely.

"If anyone offered me any high office in U.S. government, I'd be greatly honored and I'd talk to him. Certainly I would talk to Sen. Obama if he wanted to talk about it, but I think the chance of an offer are pretty slim," Nunn said.

Obama said two goals of his administration would be to secure all loose nuclear material during his first term, as well as rid the world of nuclear weapons.