An Alaska ballot measure to repeal a 2013 oil tax law that drastically cut the amount major oil companies in the state pay appeared headed for defeat.

The referendum was losing by a 52.2% to 47.8% margin, with all but six of the state's 441 precincts reporting results by Wednesday morning, but it was still too close to call, according to the Associated Press.

The No on One campaign opposed the measure to revive oil tax policies enacted under former Gov. Sarah Palin. The state's Republican and business establishments waged a $15 million campaign--funded in large part by three oil companies--to defeat the question.

Willis Lyford, a spokesman for the No on One campaign, said he expected that the results would hold and the measure be defeated once all the votes were counted.

Outspent by more than 15-to-1, supporters of the ballot question wanted to revert to the old oil-tax structure that featured progressive taxes when oil prices rose. The 2013 law backed by state Republicans carried a flat tax on revenues.

Mrs. Palin, who favored reverting to the oil tax structure she signed into law in 2007, wrote in favor of approving the measure on her Facebook page and posted an 18-minute video defending her position on her website. But she declined or ignored invitations to appear in public on behalf of the campaign to revert to the policy she enacted as governor.

A spokesperson for the Yes on One campaign didn't return calls or emails seeking comment.

Write to Zusha Elinson at zusha.elinson@wsj.com

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