The two sides spent more than $10 million -- unprecedented for such efforts in Alaska -- and throughout it all, the state's highly popular first-term governor, Sarah Palin, held back. Alaska law forbids state officials from using state resources to advocate on ballot initiatives.

Then, six days before the Aug. 26 vote, with the race looking close, Palin broke her silence. Asked about the initiative at a news conference, she invoked "personal privilege" to give an opinion. "Let me take my governor's hat off for just a minute here and tell you, personally, Prop. 4 -- I vote no on that," she said. "I have all the confidence in the world that [the Department of Environmental Conservation] and our [Department of Natural Resources] have great, very stringent regulations and policies already in place. We're going to make sure that mines operate only safely, soundly."

Palin's comments rocked the contest. Within a day, the pro-mining coalition fighting the referendum had placed full-page ads with a picture of the governor and the word "NO." The initiative went down to defeat, with 57 percent of voters rejecting it.

Three days later, Palin was named Republican Sen. John McCain's running mate, throwing Alaska into a media frenzy. But the fallout has lingered from an episode that may stand as one of the most consequential in Palin's 21-month tenure. The state ethics panel is examining whether her comments violated the law against state advocacy on ballot measures; it had already ruled that a state Web site was improperly slanted toward mining interests.

Opponents of the referendum say Palin's intervention showed her willingness to speak up for what she saw as the state's best interests, even if it upset many Alaskans. "It was very positive," said John Shively, chief executive of Pebble Partnership, a consortium of Vancouver-based Northern Dynasty and multinational mining giant Anglo American that is planning the mine. "She's very popular as governor, and so it certainly never hurts to have a popular governor on your side."

The initiative's supporters, stunned by Palin's late intervention, say it demonstrated her bias in favor of development, even when it threatens an industry that supports thousands of Alaskans -- including Palin's husband, Todd, a part-time commercial fisherman who grew up near Bristol Bay.

For Palin to intervene as she did, with a brief, seemingly off-the-cuff statement just days before the election, also showed a lack of serious engagement on complex and important issues, initiative supporters say. Palin, they say, was simply going on the word of officials in her administration that the existing regulations sufficed, without taking into account their possible biases: Her natural resources commissioner hails from the mining industry, and mining companies directly subsidize some regulators' salaries.

"She has this great faith that nothing will go wrong, which gave her a false sense of security, so she went off a little half-cocked" and spoke out, said Tim Bristol, Alaska program director for Trout Unlimited.

McCain campaign spokeswoman Meghan Stapleton, Palin's former press secretary, defended the governor's intervention. "From the moment Governor Palin took office, she made it clear she supports responsible resource development," Stapleton said. "On the issue of the possible development of Pebble Mine -- this is not about whether you are for or against development, because they haven't even submitted a permit; this is about process and ensuring that any company that wants to come to Alaska and develop our resources is at the very least provided the opportunity to avail themselves of the state's process."

Most irksome to initiative proponents was Palin's effort to cast her intervention as "personal."

"We were just like, 'When does she have her hat on and when does she have it off?' " Bristol said. Former governor Tony Knowles, a Democrat who lost to Palin in 2006, went further and said she may have violated the law against using state resources to advocate on initiatives. He said he never took such a decisive stand on a ballot initiative.

"She says, 'I'm going to take off my governor's hat,' but the only reason the press was there was that they were called to a press conference by the governor," he said. "Being governor is not a costume -- you either are the governor or not."

Shively said it is "absolute balderdash" to question Palin's right to oppose the measure. Yet some other opponents of the referendum said they were surprised she spoke out. "I was delighted, absolutely delighted, but I don't know if it was the right thing for her to do," said Cynthia Toohey, who co-owns an Alaska mine and chaired the opposition coalition. "I've lived in the state 30 years, and I don't believe I've ever heard a governor come out for or against an initiative like that."

The same week that Palin voiced her views, Alaska's Public Offices Commission ordered revisions to an informational Web site set up by the state. The site stated that the initiative's proposed new regulations were "general and less precise" than existing law and that they might lead to limiting operations at existing mines. Initiative supporters said the Web site echoed the mining industry's talking points.

Mining companies are proceeding with planning for Pebble Mine and hope to apply for permits in a year. Discovered in 1988, the site is the largest gold and copper deposit in the country. Supporters, who include many Native Alaskan leaders, say the mine would provide jobs for struggling rural Alaska and note that mining yields $200 million a year in state tax revenue.

But the mine would sit on Bristol Bay, a fishing paradise where 31 million sockeye salmon worth $108 million were caught last year. Opponents consider it too risky to construct an open-pit mine, as well as the world's largest dam to hold mining waste, so close to the valuable fishing grounds. The defeated initiative would have addressed their concern, barring any new large metals mine from releasing chemicals that would damage salmon, a standard not included in current law.

Fishing employs more people than any other Alaska industry -- 12,000 mostly seasonal jobs in Bristol Bay alone, compared with 5,500 mining jobs statewide. But the mining industry has more lobbying clout. In the referendum fight, the pro-mining coalition easily outspent its opposition.

Mining interests have courted Palin since her inauguration. Northern Dynasty contributed to her inaugural fund, and other mining companies have offered gifts and paid travel expenses for Palin's husband to go on fact-finding trips.

Palin suggested in her campaign and early in her tenure that she would withhold judgment on Pebble Mine. In a campaign questionnaire, she said that "as part of a Bristol Bay fishing family myself, I would not support any resource development that would endanger the most sensitive and productive fishery in the world." In a September 2007 interview with the Anchorage Daily News, she repeated that "Pebble Mine will not be permitted on our watch" if it hurts the salmon grounds, but she added that "we can't go in there with a preconceived notion that Pebble Mine should or shouldn't be permitted."

Environmentalists saw a bad omen when Palin's administration urged legislators not to toughen a regulation that the previous governor, Frank Murkowski (R), had loosened to allow some levels of toxicity in streams when salmon are not present. Political strategist Danny Consenstein, a leader of the pro-initiative team, said he suspected that Palin eventually came out against the initiative to maintain her Republican standing in a state where the party has long supported the use of natural resources.

"This is kind of a litmus test," he said. "If you're against the mining industry, you're anti-Alaskan. She's a Republican governor, and she's got to show she's pro-development."

A week before the vote, Palin spoke with initiative opponent Mead Treadwell, the chairman of the U.S. Arctic Research Commission. He sensed that the governor was seeing things his way. "Palin said, 'I can't take a position, but if anyone asks me what I think, I'd say that I don't like it,' " Treadwell recalled. "And about an hour later, someone asked her."

She stated her opposition without warning Rick Halford, a conservative Republican and former state senator. A main initiative supporter, he had worked hard for Palin's election. The two had talked during the summer about Pebble, and "she was cautious and trying to figure it out at that point," he said.

Art Hackney, a political consultant and director of Alaskans for Clean Water, speculated that Palin may have been irked by complaints about the biased language on the state Web site. "It was her way of waving her wand, as she is wont to do," he said, ". . . and poof, undercut this effort with one fell swoop."

Staff writers Steven Mufson, Amy Goldstein, James Grimaldi and Robert O'Harrow contributed to this report from Washington.