Obama's campaign and those of his Democratic rival, Hillary Clinton, and Republican John McCain all bickered over whether it was a good idea to suspend for the summer the 18.4-cent federal tax on a gallon of gasoline.
Clinton and McCain support the move but Obama says it is the wrong way to approach long-term energy policy.
With Indiana and North Carolina to hold contests next Tuesday, Obama focused on gas prices and the weakening job market as he campaigned in Indiana.
His shift to economic issues came after Obama denounced his former pastor, the Rev Jeremiah Wright, saying he was appalled by Wright's recent appearances in which he repeated charges that the US Government deserved some blame for the September 11 attacks and had a hand in spreading Aids to blacks.
"The situation with Reverend Wright was difficult. I won't lie to you," Obama told a participant at an Indianapolis round-table.
"But frankly what he said over the last few days, and in some of the sermons that have been excerpted, were unacceptable and weren't things that we believed," he said.
"And what we want to do now though is to make sure that this doesn't continue to be a perpetual distraction."
ROILED CAMPAIGN
The Wright controversy roiled Obama's campaign for weeks as he grappled with questions over his ability to attract white working-class voters who lean Democratic but are considered important "swing" voters in the general election in November.
A New York Times/CBS News poll published on Wednesday showed the number of Democratic voters expecting Obama to win his party's nomination had fallen sharply over the past month after the uproar over Wright and Obama's loss of the Pennsylvania primary to Clinton.
