Updated

Republican Gov. Frank Murkowski is fighting to survive Tuesday's primary after a rocky first term and a campaign in which opponents have tried to blame him for the partial shutdown of the nation's largest oil field.

Murkowski is polling last in the three-way race for the GOP nomination. The winner will likely face Democrat Tony Knowles, a two-term former governor, in the general election.

Elections were also being held Tuesday in Wyoming and Oklahoma.

Murkowski, 73, has tried to turn the election into a referendum on his proposal for a $25 billion natural gas pipeline to Canada, calling the project "the greatest significant event since statehood."

If a different Republican nominee emerges, "it will be very difficult to get his contract moved forward," said Alaska House Majority Leader John Coghill, a Republican.

Murkowski's approval ratings have skidded over the past four years because of much-criticized decisions such as appointing his daughter Lisa to his U.S. Senate seat and purchasing a state jet after his request for the aircraft was denied by both the federal government and state Legislature.

A statewide poll by the Dittman Research Corp. showed Murkowski with 17 percent, compared with 40 percent for former Wasilla mayor Sarah Palin and 29 percent for former state legislator John Binkley of Fairbanks. The survey of 514 people was taken Aug. 7 to Aug. 13 and had a margin of error of plus or minus 4.3 percent.

Knowles is expected to easily beat two lesser-known primary opponents. He has been quietly raising cash and waiting for a Republican opponent to emerge.

In the campaign's final days, Murkowski has been stung by the partial shutdown of the Prudhoe Bay oil field, where production was cut in half earlier this month because of leaks and pipeline corrosion. The governor's opponents accuse his administration of allowing the oil company BP PLC to go years without proper maintenance of its facilities.

Murkowski has pledged to hold BP accountable, but he insists state government should not be in the business of physically monitoring the company's facilities.

Alaska voters also will decide Tuesday whether to institute a $50 per-person tax on cruise ship passengers. Proponents want the industry to pay its fair share with an estimated $50 million a year in revenues aimed at improving ports and harbors and other visitor services.

The cruise ship industry has spent nearly $2 million to defeat the measure.

In Wyoming, popular incumbent Gov. Dave Freudenthal, a Democrat, faces a half-hearted challenge from Al Hamburg, a retired house painter whose 1989 conviction for election fraud will prevent him from holding office even if he manages to win.

On the Republican side, attorney and rancher Ray Hunkins — who lost in the 2002 primary — is a strong favorite over John Self, who did not attend the state Republican convention and has spent just $1,600 on his campaign.

U.S. Rep. Barbara Cubin, a Republican, is being challenged by political newcomer Bill Winney, a Navy officer.

In Oklahoma, Lt. Gov. Mary Fallin was favored to win a runoff against Oklahoma City Mayor Mick Cornett for the GOP nomination to succeed seven-term Republican Rep. Ernest Istook. Istook is leaving the House to run for governor against popular incumbent Brad Henry.