Rep. Bernie Sanders’ (I) unofficial Senate campaign got a boost over the weekend when Vermont Gov. Jim Douglas (R) announced that he will not try to succeed retiring Sen. Jim Jeffords (I) next year.

Douglas was seen as the GOP’s best hope of regaining the seat it held until Jeffords bolted the party in 2001 over disagreements with President Bush’s policies on the environment and education. His decision is the second domino to fall — following Jeffords’ retirement announcement last month — in what could be a wild 2006 election in the Green Mountain State.

Attention has now turned to Lt. Gov. Brian Dubie, who must decide whether to seek another two-year term as the state’s No. 2 or the Republican Senate nomination.

He is also considered a potential House candidate, as Sanders will vacate the state’s lone seat to go after the Senate opening.

“Douglas would have been the strongest Republican candidate,” said Eric Davis, a political science professor at Middlebury College in Vermont. “There’s a number of Republicans who expressed interest in the job,” including IDX Systems Corp. co-founder Richard Tarrant and wealthy businessman and failed 2004 Senate nominee Jack McMullen.

But without a big name like Douglas to clear the field “there probably will be a Republican primary in September 2006,” Davis predicted.

That gives Sanders the benefit of being able to run nothing but a general election race from the start.

“Now Bernie can run for the general election and Republicans will have to campaign against each other until nine weeks before Election Day,” Davis said.

Republicans downplayed the impact Douglas’ decision to seek another term as governor will have on their Senate chances.

“There’s still some top-tier candidates considering it, and we’re hopeful that one of them will get in the race and we still believe it will be a competitive race,” said Brian Nick, the National Republican Senatorial Committee’s spokesman.

Jim Barnett, chairman of the Vermont Republican Party, remained optimistic too: “I’m hoping we can avoid a divisive and costly primary.”

Davis said that Douglas had more going for him than just name recognition and the governorship.

While Dubie is a conservative Republican, Douglas is a moderate, very similar to the kind of Republican that Jeffords was before he left the GOP, and that is the kind of Republican who does well in Vermont, Davis said.

“I’m not sure the people of Vermont want to be represented by ‘a George Bush fighter pilot Republican,’” Davis said, referring to a description Dubie gave of himself to a local newspaper.

Bush lost to Sen. John Kerry (D-Mass.) by 20 points in Vermont in last year’s presidential contest.

While pundits now give Sanders the edge, despite not knowing who his opponent will be next year, his spokesman played down any sense of inevitably surrounding the self-described socialist’s nascent campaign.

“Clearly there’s going to be a strong Republican candidate and they’re going to have millions and millions of dollars,” said Jeff Weaver, Sanders’ chief of staff. “It’s going to be a hot race [yet] we’re confident he’s going to win — but it’s not going to be easy.”

Observers agree that a candidate such as Tarrant would be able to pour millions of dollars of his own money into a race, automatically making the contest competitive.

Despite earning favorable comments from Senate Minority Leader Harry Reid (D-Nev.) and Democratic Senatorial Campaign Committee Chairman Charles Schumer (N.Y.), national Democrats still dance around the issue of whether the party will get behind Sanders.

“Our goal is to make sure we have the best possible person to succeed Sen. Jeffords and someone who shares his values and independence,” DSCC spokesman Phil Singer said.

There are Democrats in Vermont who continue to harbor ill will toward Sanders for his stoking of the Progressive Party, which usually wins support in statewide, legislative and local elections at the expense of Democrats.

Douglas and Dubie both have benefited from seeing the majority left-leaning vote split between Democratic and Progressive challengers in past races.

The base Republican vote in Vermont “is about 40 percent,” so three-way races have allowed Republicans to “squeeze” into office, Davis said.

That makes it imperative to keep a Democrat out of the Senate race and a Progressive out of the House race if liberal candidates are to win, Democrats concede.

“I think all the signals from Washington are that the Democratic Party is supporting Bernie Sanders in the Senate race,” Davis said. In turn, “Democrats will try to keep a Progressive out of the House race as a deal,” he added.

A Vermont television station reported over the weekend that Rep. Barney Frank (D-Mass.) said that just such a deal had been struck. But Frank said in an interview Monday that while he agrees with that strategy, he does not know of any formal deal between the parties.

“That’s my inference,” Frank said. “There is no actual ‘deal’ that I know of.”

Frank said that if a Democrat wants to challenge Sanders, no one can stop him but that it would not be helpful to Sanders and would not be smart strategically if both Democrats and Progressives ultimately want to deny Republicans the Senate seat.

Sanders said it is too early to officially launch a campaign.

Dubie said he is seriously considering the Senate race, but no one expects a decision before the state Legislature adjourns later this summer.