BOISE - Republican Gov. Butch Otter has been called plenty.

Libertarian. Capt. William Call, his favorite character in the "Lonesome Dove" novel. Even "Mr. Tight Jeans," for winning a barroom contest in the 1990s. But "tax and spend" Butch?

His best-known rivals in the May 25 GOP primary, Ada County Commissioner Sharon Ullman and former elk rancher Rex Rammell from Rexburg, contend Otter is vulnerable after his failed 2009 plan to raise Idaho's gas tax, hike vehicle registration fees and other driving-related surcharges by $174 million.

Rammell and Ullman, who are both courting the tea party movement for support, say Otter's push to boost taxes during a deep recession shows he's lost touch with those who elected him, instead siding with special interests like the construction industry.

In March, Otter rehabilitated himself among some conservatives by leading a lawsuit against the federal government challenging President Barack Obama's health-insurance reforms.

But Ullman points out Otter still has a 15-person task force meeting on unresolved transportation funding issues.

That panel could again recommend raising gas taxes and fees - after the November general election.

"If he gets re-elected, which Butch Otter do we get?" said Ullman. "The 2009 'tax and-spend' version, or the 2010 'no new taxes' version? I don't think voters should have to take the chance of getting the 2009 version back."

Otter, in elected office since 1987, including stints as lieutenant governor and U.S. representative, has five primary foes: Walt Bayes, a perennial candidate and abortion foe; Tamara Wells, of Post Falls, who promises to "detaxify" Idaho; suspenders-clad Pete Peterson, who is selling underwear on his campaign website; and Ullman and Rammell.

In 2008, Rammell ran a failed independent campaign against Jim Risch for U.S. Senate perceived by many as a personal vendetta. Risch, as temporary governor in 2006, had sent wildlife agents to kill Rammell's escaped elk.

He announced his campaign against Otter for governor in April 2009, just as Otter's standoff with conservative Republicans in the Idaho House over the gas tax hike was escalating. Otter vetoed dozens of bills and held lawmakers hostage in Boise in a failed bid to twist their arms.

Rammell, now touring Idaho towing a 16-foot green-and-yellow dinosaur, says Otter's push to hike taxes convinced him he'd made the right move.

"He opened the door to defeat with his gas-tax debacle," Rammell said. "No conservative in their right mind would support raising taxes in the middle of a recession."

Otter, who has declined to debate opponents before the May 25 primary, has heard from some prospective voters about the 2009 tax fight, concedes Debbie Field, his campaign manager.

"It's people who probably will be a percentage that will vote for Sharon or Rex," Field said. "But it's easy to posture, without some reality."