WASHINGTON (CNN) -- Sen. John McCain sought to remind Pennsylvanians on Wednesday about Sen. Barack Obama's controversial remarks on "bitter" small-town voters during the Democratic primaries.
And Democrats seized on a comment of McCain's that the date when U.S. troops could start leaving Iraq was "not too important."
At a town hall-style meeting in Philadelphia, McCain said he doesn't agree that voters in Pennsylvania "cling to their religion and the Constitution because they are bitter. I am going to tell them that they have faith and they have trust and support the Constitution of the United States because they have optimism and hope and that is the strength of America."
McCain was referring to remarks Obama made before the state's April 22 primary that decades of lost jobs and politicians' unfulfilled promises have left some small-town voters "bitter" and clinging "to guns or religion or antipathy to people who aren't like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations."
Democrats pounced on McCain's remarks on troop withdrawals soon after he made them Wednesday on NBC's "Today" show.
McCain was asked whether he had an estimate of when troops could begin coming home.
"No, but that's not too important," McCain said. "What's important is the casualties in Iraq. Americans are in South Korea. Americans are in Japan. American troops are in Germany. That's all fine. American casualties and the ability to withdraw; we will be able to withdraw."
Sen. Joe Biden, chairman of the Senate Foreign Relations Committee and a former 2008 presidential candidate, said in a statement, "Sen. McCain's comment is evidence that he is totally out of touch with the needs of our troops and the national security needs of our nation. I think many of our brave soldiers and their families would disagree that it's 'not too important' when they come home."
In a conference call Wednesday, Sen. John Kerry, an Obama surrogate and the 2004 Democratic presidential nominee, said McCain consistently confuses facts about the war.
"It is unbelievably out of touch and inconsistent with the needs of Americans and particularly the families of troops who are over there," the senator from Massachusetts said. "To them it's the most important thing in the world when they come home. It's a policy for staying in Iraq."
McCain spokesman Tucker Bounds countered that the Obama campaign was launching "a false attack."
At the town hall meeting, McCain talked up his energy policies, namely how to beat the oil crunch plaguing millions of Americans.
"I will lead this nation in a mission ... a mission that overtime will reduce our dependence on foreign oil. We can do it," he said. "America is the center of innovation of technology progress."
McCain urged research into wind, tide, solar and nuclear technologies as alternative fuel sources.
The senator from Arizona also took time out to blast Obama on economic issues, namely taxes.
"Why in the world would anyone consider raising your taxes in difficult economic times? Sen. Obama wants to raise capital gains tax. My friends, there's a hundred million people who have some kind of investment that is affected by capital gains," he said. "Why would we want to take more of the people's money and send it to Washington to spend on a bridge in Alaska to an island with 50 people on it?" Watch McCain on the economy »
McCain also called on Obama to appear alongside him in a series of town hall meetings across the country.
Meanwhile, the presumptive Democratic nominee is in the midst of a two-week economic tour across the country.
In Chicago, Illinois, for a round-table discussion Wednesday, Obama brought up the credit crunch facing millions of Americans -- and took aim at McCain, saying he is "part of the problem, not part of the solution."
"When he had a chance to help families avoid falling into debt, John McCain sided with credit card companies. When he had the chance to protect teenagers and college students from deceptive credit card practices, he sided with the credit card companies," he said. Watch more of Obama's speech »
"I fought against the credit card industry's bankruptcy bill that made it harder for working families to climb out of debt. He supported it. He even opposed exempting families who were only in bankruptcy because of medical expenses they couldn't pay."
CNN's Alexander Mooney contributed to this report.