As Ms. Palin takes to the road to campaign with Mr. McCain, invoking the pipeline as a major victory, some Alaska lawmakers who initially endorsed her plan now believe it was a mistake. State Senator Bert Stedman, a Republican who is co-chairman of the finance committee, said that in its contract with the chosen developer, TransCanada, the state bargained away too much leverage with little guarantee of success.

“There is no requirement to lift one shovel of dirt or lay down one inch of steel,” he said.

A spokesman for Ms. Palin, Bill McAllister, denied that her recent statements about the pipeline were misleading. He said they should be viewed within the context of the project’s long and frustrating history, dating back to the Carter administration.

“When the governor signed the legislation giving her administration the authority to grant the gas line license to TransCanada, Alaska came closer than it has ever been to seeing the project actually happen,” Mr. McAllister said. “There is no denying that a major milestone in the project has been reached.”

Ms. Palin’s pipeline plan has its roots in longstanding efforts to access the trillions of cubic feet of natural gas under the North Slope, where some of the world’s major oil companies, including BP, Exxon Mobil and ConocoPhillips, have exploration and development rights. Congress has prodded all parties involved to develop a plan to tap the gas since at least the 1970s, but the private sector has been unwilling to assume the huge cost of building a pipeline without considerable government tax breaks and other concessions.

Ms. Palin’s push for a pipeline is central to her view that Alaska, with its North Slope gas resources, is a key to helping the United States develop an energy policy that embraces increased domestic production of gas and oil and the development of renewable and alternative energy sources.

Her predecessor, Frank H. Murkowski, had negotiated an exclusive pipeline deal with the major oil producers that proved unpopular with lawmakers and was never acted on. In the 2006 Republican primary, Ms. Palin wielded Mr. Murkowski’s pipeline proposal against him, calling it a sweetheart deal for Big Oil, which treated Alaska like a colony and faced little resistance from past governors.

Once elected, Ms. Palin set about fashioning an alternative that was essentially a 180-degree turn, intended to open up the bidding process to other companies. It also did away with incentives that a consultant for the Legislature estimated would have saved the oil companies an estimated $10 billion over 30 to 40 years. Ms. Palin also rehired key state oil and gas officials, including Marty K. Rutherford, who had quit, and Tom Irwin, who had been fired, after opposing Mr. Murkowski’s approach.