Obama's stance was backed up by 230 economists who released a letter Monday opposing the gas tax holiday. The signers included four Nobel Prize winners and economic advisers to presidents of both parties.
Late Monday, Clinton acknowledged the difficulty of getting such a gax-tax suspension enacted in the next few weeks. "Realistically, it's tough," Clinton told reporters on her campaign plane.
A CNN-Opinion Research Corp. poll released Monday found six in 10 saying gas prices have caused financial hardship for their families. Eight in 10 said they consider it likely they'll be paying $4 a gallon sometime this year, and nearly half said they expect prices to hit $5 per gallon.
Any belt-tightening didn't extend to the presidential campaigns, with Obama outspending Clinton in both states. By Clinton campaign estimates, Obama has spent $5.6 million in Indiana to Clinton's $3.2 million. In North Carolina, the Clinton campaign said, Obama has spent $4.9 million to Clinton's $3.5 million.
Both candidates have had supporters spending money in Indiana as well. The Service Employees International Union, which is backing Obama, spent about $1.1 million in the state, much of it on ads. The American Leadership Project, which has received most of its money from labor groups backing Clinton, spent more than $1 million on ads in Indiana that questioned Obama's economic policies.
North Carolina and Indiana are important because they are the largest states left to vote, but they cannot mathematically settle the nomination. A candidate needs 2,025 delegates to win, and Obama had 1,745.5 to Clinton's 1,608 Monday.
Obama continued to close Clinton's long-held lead among superdelegates, those party leaders who aren't bound by the outcome of state contests. He picked up two from Maryland Monday, leaving him trailing Clinton 269-255.
Obama campaigned in both Indiana and North Carolina on Monday, closing the day with an outdoor rally on American Legion Mall in Indianapolis headlined by Stevie Wonder.
Wonder opened his act by doing musical scales unaccompanied, using Obama's name as he went up and down the register before encouraging the crowd of thousands to join and follow him.
"Barack Obama inspires me to write songs ... and encourages me that we can come together and be a far greater country than ever before," Wonder said. He sang a series of hits, including "Signed, Sealed, Delivered I'm Yours," one of the Obama campaign theme songs.
Clinton's main hope for winning the nomination is to persuade most of the roughly 220 superdelegates still undecided to disregard his lead in the delegate chase and support her instead. The Clinton campaign also hopes to get a boost by getting delegates from Michigan and Florida seated.
The Democratic National Committee disqualified those delegates last year because the two states held their primaries too early. Clinton won both contests after all the candidates pledged to boycott the campaigns.
The DNC's Rules and Bylaws Committee has scheduled a meeting May 31 to consider seating delegates from the two states. Asked about a report over the weekend in the Huffington Post that the Clinton campaign is encouraging supporters on the committee to reseat the delegations, Clinton spokesman Howard Wolfson said, "If it's a secret that we want the delegations from Florida and Michigan seated, it's the worst kept secret in American politics."