(CNN) -- Sen. Barack Obama told voters in Wayne, Pennsylvania, on Saturday that he'll cut taxes for the middle class, raise taxes for the wealthy and pour more money into what he calls green energy.
Later Saturday, in Illinois, Obama helped fill sandbags near the Mississippi River in an area devastated by flooding, his campaign said. The same day, Sen. John McCain extended his sympathies to those affected by flooding in the Midwest.
According to his campaign, Obama wants to invest $150 billion over the next 10 years to establish a green energy sector; create a national low-carbon fuel standard to ensure that the fuel is more efficient, and invest in clean energies like solar, wind and biodiesel.
That, according to the campaign, would create up to 5 million new green energy jobs.
"He isn't offering any solutions to help Americans pay for high gas prices. Instead, he's proposing a gas tax holiday that's nothing more than a Washington stunt," Obama said. "I was for the idea back then, but I've learned from my mistake, because I don't think it's right to say you're offering families relief when you're just boosting oil company profits."
Obama says McCain's gas tax plan would "actually do real harm" and take "$3 billion a month out of the highway trust fund and hand it over to the oil companies."
Doug Holtz-Eakin, the McCain campaign's senior policy adviser, told reporters in a conference call Thursday that McCain "is not out of touch with the pressure on gasoline prices. He proposed a gas tax suspension for the summer that would put $600 in the pocket of a trucker buying diesel fuel, take some of the pressure off the price increases of all the things that they deliver, help American families get through the summer."
The Illinois senator says taking money from the highway fund would have negative economic effects, especially for Pennsylvanians.
"And at a time when the unemployment rate is rising faster than at any point in the past 20 years, this idea would cost another 300,000 jobs in the construction industry, including more than 11,000 right here in Pennsylvania," he said.
Obama's plan for relief includes putting a windfall profits tax on oil companies, using the proceeds to help Pennsylvania families pay their heating and cooling bills. He also wants to increase transparency in the way prices are set, "so we can make sure that energy companies aren't bending the rules," according to his campaign.
And on taxes, Obama blasted the McCain campaign for painting him as a tax-and-spend liberal.
"The general strategy ... was to go after Democrats by saying, 'Ah, they're tax and spend. He wants to hike your taxes.' I'm amazed how people can get away with saying some of this stuff with a straight face," he said. "[McCain campaign adviser] Carly Fiorina was on the television the other day saying Barack Obama will not cut taxes for anybody. This is what she said. I mean she just said it right to the screen."
Obama said his tax plan would give "every middle-class family a $1,000 tax cut." In addition, his plan aims to eliminate income taxes for seniors who make less than $50,000 a year.
Obama also praised this week's Supreme Court decision giving detainees at Guantanamo Bay, Cuba, the right to push for their release, and he offered history as a way to justify it.
"During the Nuremburg trials, part of what made us different was even after these Nazis had performed atrocities that no one had ever seen before, we gave them a day in court that taught the entire world about who we are, but also about principles of the rule of law," he said. "Now, the Supreme Court upheld that principle. ... John McCain thinks the Supreme Court was wrong. I think the Supreme Court was right."
On Friday, McCain called the Supreme Court decision one of the worst in history. Watch McCain take on the Supreme Court's decision »
"I think the United States Supreme Court is supposed to act not on their views of the performance of an administration, but on the most important issues affecting, or how to implement best, the Constitution of the United States. I just am convinced that to treat enemy combatants, who are not citizens, and give them the same rights as an American citizen ... is a decision that will harm our ability to detain and prosecute individuals who are enemy combatants who want to destroy America," he said in an interview.
On Saturday, McCain, meanwhile, took part in what his campaign calls a "virtual town hall" conference call, which is designed to reach out to Democrats, independents and female voters.
The conference call, which took place Saturday afternoon, included former supporters of New York Sen. Hillary Clinton, the campaign said.
Also on Saturday, McCain issued a statement about the Midwest flooding, saying, "Our thoughts and prayers go out to all those impacted by the flooding throughout the Midwest. Cindy and I would like to extend our sympathies to all those who have lost loved ones, and stand ready to help those in the Midwest to recover and rebuild."
After Saturday's town hall in Wayne, Obama headed to Quincy, Illinois, which has been affected by devastating flooding. The campaign says he helped fill sandbags near the Mississippi River. Watch Obama take part in a sandbagging effort »
Volunteers and emergency workers have been placing sandbags around stores and businesses in the area, and are trying to protect the local water treatment plant. The city is preparing for floodwaters that could top the 1993 all-time high level seen there.
Obama's Senate office released a letter he signed, along with the Illinois congressional delegation, asking for the Federal Emergency Management Agency and the Army Corps of Engineers to help prepare for rising water in areas like Quincy.
CNN's Chris Welch and Steve Brusk contributed to this report.