MANCHESTER, N.H. -- The fate of Seabrook, a $4.9 billion nuclear power plant on the verge of bankruptcy, is rarely mentioned in presidential campaigning around the nation, but here in New Hampshire, site of the first primary and the power plant, it has become a sharply divisive issue among Republican presidential candidates.

For Democrats, the issue is an easy one: They are all against. But the Republican contingent is in a different position, forced to seek a balance between the party's generally pro-nuclear power stance, local fears over safety and guaranteed voter anger over the threat of major rate hikes to pay construction costs.

The controversial plant, which has yet to produce a watt of power, produces only opposition on the Democratic side. "To be a viable Democratic candidate, you have to be right on Seabrook," said Mark Longobough, manager of the campaign of Rep. Richard A. Gephardt (D-Mo.). "It's not which side you're on, but how much you're against it," Paul Tully, political director for Massachusetts Gov. Michael S. Dukakis said.

For Republicans, the opposite is true. "It is an extremely touchy issue for Republicans. It is an article of faith that you can't be opposed to nuclear power per se, and everyone at least says they are for allowing Seabrook to go on line. But after that, it's open season," a state Republican aide said.

Seabrook has been a major controversy in New Hampshire politics since the early 1970s, when it was proposed. It is now coming to a head in time to become a major factor in the Feb. 16 presidential primary for a number of reasons.

The majority owner, Public Service Co. of New Hampshire (PSNH), is seeking federal approval to start up the plant despite refusal of Massachusetts officials to draft evacuation plans on grounds that an evacuation during a disaster would be impossible. At the same time, PSNH is on the verge of bankruptcy. And finally, PSNH has asked for a 15 percent rate rise, an increase opponents of Seabrook contend represents a fraction of the fees consumers would have to pay for construction if the plant's switch is turned on.

All these concerns have been compounded by the recent disclosure that the top five PSNH management officials have been granted "golden parachutes" if the utility defaults on obligations. The utility president's "golden parachute" would be worth as much as $700,000.

In the Republican debate over Seabrook, the two extremes are represented by former Delaware governor Pierre S. du Pont IV and Rep. Jack Kemp (N.Y.). "Turn it on," is the way Fred Maas, du Pont's New Hampshire manager describes du Pont's policy. Kemp, on the other hand, has discovered a way to mesh conservative support of the principle of states' rights with a position designed to appeal to anti-Seabrook voters.

While theoretically in support of turning Seabrook on, Kemp backs the right of Massachusetts, the border of which is less than 10 miles away from the plant, to exercise veto power over Seabrook. The veto is sure to be exercised as long as Dukakis is governor.

Vice President Bush, whose New Hampshire chairman, Gov. John H. Sununu, is one of the leading proponents of Seabrook, has adopted an elusive stance. "He respects what the experts say," Andy Card, senior adviser to the Bush campaign, said. "It should not be a political issue whether the plant is safe. It should be up to the experts. . . . It is up to the NRC {Nuclear Regulatory Commission} to determine what is safe."

Kemp strategists, however, believe that Bush's close ties to Sununu and to Sununu's highly publicized support of Seabrook will cost him votes among moderate Republicans who are concerned about the environment and who form the base of Bush's support.

"Among Republican voters, Seabrook is extremely polarizing. They are split roughly 50-50," a Kemp organizer said, "but the intensity is with the antis." Polling data shows that roughly 25 percent of the GOP primary electorate will vote against a candidate who does not share their views on Seabrook even if the candidate is "right" on all other issues, and this 25 percent block is overwhelmingly opposed to the nuclear facility, the Kemp official contended.

In addition, these anti-Seabrook Republicans are concentrated on the New Hampshire seacoast, a stronghold of moderate Republicanism. "Seabrook is going to be a cement block around his {Bush's} neck just where he has to win big if he is going to carry the state," the Kemp strategist said. Du Pont's aggressively pro-Seabrook stand has won plaudits from the management of the Manchester Union Leader, the largest newspaper in the state and perhaps the most important endorsement in the Republican primary.

Paul Young, Kemp's campaign manager, also acknowledged that it is dangerous for a Republican presidential candidate to become associated with the anti-Seabrook forces, who are seen as liberal Democrats by the dominant conservative wing of the GOP here.

Kemp's stance has won him support among anti-Seabrook activists, including leaders of Search 88, a group pressing the candidates to spell out positions on Seabrook and nuclear power. "Kemp is the one who is out front on the Seabrook issue. He takes the best position {of the Republicans} on Seabrook," Kurt Ehrenberg of Search 88 said.

In the politics of Seabrook, local Republicans watching the candidates maneuver on the issue generally see Kemp and du Pont attempting to capitalize on Seabrook from different extremes, while Bush, because of his ties to Sununu, is caught in the middle. For the remaining three GOP candidates, Seabrook has been an issue best kept off center stage.

Sen. Robert J. Dole (Kan.), for example, said in a statement that he supports "the involvement of state and local governments," although a Dole aide said the senator has voted for legislation allowing the NRC to accept evacuation plans in the event that a state, such as Massachusetts, fails to do so.

Former secretary of state Alexander M. Haig Jr. issued a statement that said in part: "I think the best means of resolving the issue is for the NRC, state and local authorities and community groups to work out a solution that takes both citizen concerns and technological data into account."

Kerry Moody, manager of the Marion G. (Pat) Robertson campaign, said Robertson supports Seabrook, but that the issue is rarely raised.