PORTLAND, MAINE, FEB. 26 -- Republicans across Maine are holding hundreds of caucuses this weekend in a political struggle whose central theme is to preserve the established GOP against the forces of former television evangelist Pat Robertson.

Supporters of Vice President Bush in this sparsely populated state have forged an unofficial alliance with backers of Senate Minority Leader Robert J. Dole (Kan.) to beat back a last-minute charge by Robertson.

Bush, who maintains a summer home in Kennebunkport, is the clear favorite. But his supporters have been pushed into working with the local Dole camp by the possibility that Robertson workers, who have proved adept at organizing other caucus states, could embarrass them.

"A caucus is tailor-made to Pat Robertson's style of campaigning," said Ron Kaufman, Bush's New England field director.

The alliance has not been sanctioned by Dole's national campaign, which has generally benefited in states where Robertson has been strong. But state Sen. Pamela Cahill, Dole's chief supporter here, said Dole organizers have to think about protecting local party offices, which are also up for grabs at the caucuses.

"Long after the presidential campaigns are out of Maine, we're going to have to live within the party structure here," she said.

This weekend, as Republicans caucus to select 1,506 delegates to their April convention -- who in turn will choose 22 national delegates -- they will also select local party officers.

Gov. John R. McKernan Jr., Bush's top backer in the state, said he is worried that Robertson supporters will win local posts and then drop out of politics if their candidate is not elected president. "It bothers me greatly," he said.

But Robertson's backers, many at odds with the moderate Republican establishment here, say they want to win delegates and local offices in order to move the state party to the right. "There's no question that we'd like to see a change in the Republican Party here," said John Solberg, Robertson's state campaign director.

Specifically, Solberg said Robertson backers want party support for greater local control over schools and an antiabortion plank in the party platform, a move McKernan said he would oppose.

McKernan said he suggested an alliance with the Dole forces during a meeting with Cahill two weeks ago.

The first evidence of the pact came Wednesday evening, when Bush and Dole supporters combined forces in the early caucus city of Waterville and prevented a plurality of Robertson supporters from winning any of the 12 delegates at stake.

However, at a Portland caucus tonight, Dole and Bush supporters failed to agree on how to share 33 delegate slots they would have if they were to join forces against Robertson, and the delegates were selected proportionately. Bush and Robertson each won 15 delegates; Dole won three.

"It worked to a charm there," McKernan said.

Except for Bush, who made a campaign stop at the Portland jetport Wednesday, the candidates have not appeared for the caucuses. Rep. Jack Kemp (R-N.Y) has essentially written off the state.

Despite the small expenditure, Republican Party leaders say the battle between Robertson and the Bush-Dole axis is likely to produce a record turnout this weekend.

"The early caucuses show we're getting a tremendous increase in the number of people participating," said Karen Stram, who chairs the Maine Republican Party.

Solberg, the Robertson official, said formation of the Bush-Dole coalition has inspired his organizers to work even harder.

"We're going to have to get 51 percent at a lot of these caucuses or we may wind up with very few delegates," he said.

At the same time, Bush supporters are using the Robertson threat as an incentive to get their people to the caucuses.

On Thursday evening, more than 200 Republicans showed up for a caucus in the Portland suburb of Cape Elizabeth, home of Bush's daughter, Dorothy LeBlond. Few were surprised when Bush won all of the 12 delegates, but the turnout exceeded that of other years.

Although most cities and towns here are holding Republican caucuses over the weekend, the caucusing began on Jan. 31 and may continue until March 20.

The Republican Party is not keeping a delegate count. But an unofficial survey by the Bush campaign showed that, as of 11:30 p.m. , the vice president was leading with 223 delegates. Robertson had 31, 24 were uncommitted, Dole had 21 and Kemp had five.

On the Democratic side, all caucuses will be held Sunday and Gov. Michael S. Dukakis from nearby Massachusetts is favored.

But predicting the outcome for either party is a speculative business here. Registered voters with no party affiliation outnumber registered Democrats and Republicans. And an unregistered voter can caucus with either party after enrolling at a caucus site.

"I think everyone better stay tuned," Cahill said.