Clinton and certain Republican presidential nomineeare calling for a holiday on collecting the federal gas tax "to get them through an election," Obama said at a campaign rally before more than 2,000 cheering backers a week before crucial primaries in Indiana and North Carolina. "The easiest thing in the world for a politician to do is tell you exactly what you want to hear."
Clinton, who toured the Miller Veneers wood manufacturing company in Indianapolis, said "there are a lot of people in Indiana who would really benefit from a gas tax holiday.
"That might not mean much to my opponent, but I think it means a lot to people who are struggling here, people who commute a long way to work, farmers and truckers," Clinton said. She has called for a windfall tax on oil companies to pay for a gas tax holiday.
"Senator Obama won't provide relief, while Senator McCain won't pay for it," Clinton said. "I'm the only candidate who will provide immediate relief at the pump, with a plan."
In his comments, Obama was continuing a running dispute over whether ending collection of the gas tax is the quickest and best way to help consumers. Leading in delegates and the popular vote, Obama in recent days has focused on McCain, but he broadened that criticism Tuesday to include Democrat Clinton.
"Now the two Washington candidates in the race have decided to do something different," said Obama. "John McCain started it, he made the proposal, and then Hillary Clinton said 'me too."'
The plan would suspend collecting the 18.4 cent federal gas tax 24.4 cent diesel tax for the summer.
He said drying up gas tax collections would batter highway construction, costing North Carolina up to 7,000 jobs, while saving consumers little.
"We're arguing over a gimmick that would save you half a tank of gas over the course of the entire summer so that everyone in Washington can pat themselves on the back and say they did something," said Obama.
"Well, let me tell you, this isn't an idea designed to get you through the summer, it's designed to get them through an election," said Obama. He said his call for middle-class tax cuts would be far more beneficial than suspending gas tax collections.
Obama took a different view on the issue when he was an Illinois legislator, voting at least three times in favor of temporarily lifting the state's 5 percent sales tax on gasoline.
The tax holiday was finally approved during a special session in June of 2000, when Illinois motorists were furious that gas prices had just topped $2 a gallon in Chicago.
During one debate, he joked that he wanted signs on gas pumps in his district to say, "Senator Obama reduced your gasoline prices."
But the impact of the tax holiday was never clear. A government study could not determine how much of the savings was passed along to motorists. Many lawmakers said their constituents didn't seem to have benefited. They also worried the tax break was pushing the state budget out of balance.
When legislation was introduced to eliminate the tax permanently, Obama voted "no." The effort failed, and the sales tax was allowed to take effect again.
Responding to Obama's criticism, McCain campaign spokesman Tucker Bounds said the Illinois senator "does not understand the effect of gas prices on the economy. Senator Obama voted for a gas tax reduction before he opposed it."
Bounds was deliberately echoing one of Democrat John Kerry's most troublesome missteps of the 2004 presidential campaign. Kerry said of funding for the war in Iraq and Afghanistan, "I actually did vote for the $87 billion before I voted against it."
Obama and Clinton both opened their campaign day in North Carolina. Clinton toured a research facility, and collected the prized endorsement of Gov. Mike Easley.
"It's time for somebody to be in the White House who understands the challenges we face in this country," said Easley, in announcing his backing of Clinton. She then promptly headed for a string of events in Indiana.
"The governor and I have something in common - we think results matter," said Clinton.
Easley is popular with white, working-class voters that have formed the base for Clinton's success in recent primaries.
While Obama is favored in North Carolina, the race in Indiana is very tight, and Obama was heading there Wednesday.
Obama collected endorsements of his own during the day: In Kentucky, Rep. Ben Chandler, son of former Gov. A.B. "Happy" Chandler, gave Obama his backing ahead of that state's May 20 primary, and in Iowa, Democratic National Committee member Richard Machacek - a supporter of former Sen. John Edwards before he dropped out of the presidential race - switched his support to Obama.
Interest in the two primaries next week has been high. Officials in Indiana said nearly 90,000 people have cast early ballots, far outpacing absentee turnout in 2004.
At stake Tuesday are 115 delegates in North Carolina, and 72 in Indiana.