In his 1992 book, "Earth in the Balance," Al Gore described boldly where environmentalism fit in his priorities: "We must make the rescue of the environment the central organizing principle for civilization."

Eight years later, those words carry an ironic echo. As he runs for president, environmentalism has yet to emerge even as a central organizing principle of Gore's campaign--never mind his plans for civilization. Instead, improving the quality of air, land and water--an issue Gore once spoke of with almost spiritual fervor--has been at the margins of his race for the White House.

Gore usually gives the environment a passing mention during stump speeches, but the campaign has not devoted a major policy address to global warming, the subject of his book. Only last week, with the environment at last emerging as an important subject on the Democratic campaign trail, Gore aired his first television commercials on the subject. His campaign Web site has a place to click for policy statements about "The Environment," along with 31 other click-points such as "Responsible Middle-Class Tax Cuts," "Saving Our Schools" and "Protecting America's Steel Industry."

Gore's wariness about the implications of his environmental beliefs in the 2000 campaign underscores a larger tension within the candidate, according to many environmental activists and some administration officials who have worked with him on the environment and other issues. Gore the Policy Apostle can utter statements that most colleagues would regard as wildly impolitic: calling for elimination of the internal combustion engine by 2020 or denouncing excessive consumerism in Western nations as evidence of a "dysfunctional civilization." Gore the Politician, say some of these people, is prone to brooding over the electoral risks of his beliefs.

Even some sympathizers believe he has trouble merging his passion for millenarian ideas--his book calls for a "Global Marshall Plan" on the environment--with the instinctive caution that has marked his political career. Head and heart often seem out of step.

"If I was to give him one piece of generic political advice, it's to seize the moment," said Carl Pope, executive director of the Sierra Club. "He's a very well-informed and dedicated environmentalist. Sometimes I wish he would take more risks. Al Gore waits for the opening."

It is a view shared by some administration officials. "There is no one that has done a better job of raising the issue in terms of the science," said Eileen Claussen, a former assistant secretary of state who worked with the vice president on global warming. But she added: "The reality is that he hasn't been courageous."

"His first inclination is always to take the most aggressive approach," said a former administration official during the first term, who worked closely on policy with Gore at both the White House and at an agency. "But the political side of his mind turns on and makes him aware of the traps that might be sprung."

Gore's reputation--whether he should be viewed as a principled champion or a politician who talks a better game than he delivers--has taken on particular currency in recent days. The environment is a potent issue in some of the next primary states, such as Washington, which votes Tuesday, and California, on March 7. And Bill Bradley, Gore's rival for the nomination, is trying to revive his campaign by accusing Gore and the Clinton administration of repeatedly neglecting environmental interests.

Gore has now put some focus on the topic, but that has come, according to Democratic sources, only after discussions extending back a year or more about what role environmental issues should play in his strategy.

Last year, some Gore advisers were urging him to approach the issue warily. The theory then, according to participants in the discussions, was that stressing his environmental commitments would spook business interests and hinder his effort to be seen as a centrist "New Democrat." Moreover, while some environmental issues are popular--cleaning up waste sites, for instance, or protecting parks--less tangible issues such as global warming are not effective at motivating the swing voters critical to Gore's general election strategy.

When Gore was confronted with a stiffer nomination fight against the former New Jersey senator than he anticipated, it was still unclear where environmentalism fit in the strategy. Bradley has a solid environmental record: The National League of Conservation Voters gave him an average lifetime rating of 84 on environmental issues, compared to 64 for Gore. Gore's lower score reflects a more conservative voting record as a member of the House from Tennessee, when he supported a federal dam project in his state that environmentalists opposed, a point Bradley has been hitting on in recent days.

Former White House chief of staff Leon E. Panetta, a Gore supporter, said that the environment is "a gut issue" for the vice president and that it is a mistake for him to "tiptoe around these issues" on the campaign trail: "He ought to make this part and parcel [of the campaign]. This is who he is."

The candidate's comparative silence does not mean that he has forsaken environmentalism as an effective political issue, campaign aides said. Carter Eskew, a top Gore strategist, believes that environmentalism works not merely as a political issue but as a biographical one--explaining to voters what makes Gore tick. Moreover, in a general election campaign, assuming the vice president stays on his current trajectory toward the Democratic nomination, Gore plans to hammer either Texas Gov. George W. Bush or Arizona Sen. John McCain--believing that both Republicans have environmental records that leave them acutely vulnerable. "You're going to see him talking about it increasingly," said one senior aide.

But for some vocal naysayers in the environmental movement, it is not lack of talk but lack of action that makes Gore unreliable. Friends of the Earth, considered among the least compromising of environmental groups, endorsed Bradley, citing disappointment in the vice president. Other national groups that endorse candidates are staying neutral in the nominating contest.

Gore risks going into the general election criticized from both directions--as a zealot for the impolitic language in his book and as a hypocrite for his role in some administration decisions where the environmental interest was trumped by other considerations.

Bradley has criticized such decisions as the White House's 1995 bow to Republicans on a bill that allowed the clear-cutting of half a million acres of national forest; for failing to back stiffer fuel economy standards on gas-guzzling sport utility vehicles; and for extending 36 oil-drilling leases off the California coast--a charge the Gore campaign calls unfounded because the extensions have yet to be decided by the Commerce Department.

Bradley also has knocked the administration for failing to speed up the elimination of methyl bromide, a substance that depletes the ozone layer, and for slowing the implementation of the 1996 Food Quality Protection Act, which was designed to protect children from toxic chemicals. On both issues, said Environmental Protection Agency Administrator Carol M. Browner, a Gore protege: "They're just wrong. We are doing exactly what the law . . . required us to do. It may be taking a little bit longer than we thought, but you know what? Sound science doesn't run on time."

Within the Gore political team, there is vast resentment toward the environmental lobby, whose leaders are seen as the most clamorous, and least grateful, of any special interest. How, Gore sympathizers ask, can activists let their disappointment in individual decisions obscure the larger picture--that the vice president has been their most influential friend ever? "They're winning the argument, but they sometimes won't take yes for an answer," said one White House official close to Gore's campaign. "They have been harder on Gore than they have any reason to be."

Under the Clinton administration, more wilderness has been put under federal protection than in any administration since those of Theodore Roosevelt and Franklin D. Roosevelt, heroes of the conservation movement. The administration beat back an attempt by the new GOP congressional majority to dismantle environmental protections and has budgeted new money for enforcement of clean air and water laws.

"Until this administration, we really didn't have access to government," said John Adams, a dean of the environmental movement who heads the Natural Resources Defense Council and has endorsed Gore. "We have had more impact and better results in this administration than we ever had before."

Part of the problem for Gore lies in the nature of his job as vice president.

Environmentalists expected him to be a consistent advocate. Just as often, however, it fell to Gore to play the role of broker, helping Clinton oversee a policy process in which the environmental interest would not always trump competing needs.

"He's not running for president as Mr. Greenjeans," said one administration veteran who has worked on environmental issues and is assisting Gore's team. "He's green, but I don't think he's green at all costs."

Perhaps the most pivotal episode in which Gore tried to balance competing interests came in 1997, when he flew to Japan and was the key player during the negotiation of the Kyoto agreement on global warming.

Kyoto divided administration policymakers like few other issues. Environmental officials and outside groups were determined that the United States agree to a treaty with tough limits on the emission of greenhouse gases. Economic officials including Lawrence H. Summers, now treasury secretary, warned that such an agreement could have grievous consequences for the economy. Gore's political advisers were nearly unanimous in their warnings about the potential negative consequences of the issue.

In particular, they wanted him not to travel to the summit, where it seemed possible the conference would end with no agreement or with one that would prove unpopular at home. Sources said the late Robert Squier, one of Gore's political advisers, came to one meeting armed with polling data and a plea--this issue could kill you.

In the end, after what sources described as agonizing deliberations, Gore did go. The Kyoto agreement, as some administration officials see it, represented an artful splitting of differences. With Gore at the negotiating table, the United States agreed to reducing greenhouse gas emissions by 7 percent below 1990 levels by 2012. That was a steeper and faster reduction than Clinton's economic advisers wanted. But the target levels were not accompanied by binding restrictions until after 2008--which critics called a major weakness.

Kyoto has become a symbol of Gore's style--with different meanings for different people. "It shows his deep convictions, and his willingness to act on them--even in the face of risk," said David B. Sandalow, a former White House and current State Department official who was at Kyoto. But environmentalists note that the administration since then has done little to build support for the treaty's passage or to reduce U.S. emissions.

"Our own emissions have gone up," said John Passacantando, executive director of Ozone Action. "All I've worked on for seven years is ozone depletion and global warming, two key issues of Al Gore's. Dealing with him in this administration is no different than dealing with any other politician. If you don't push them and agitate every day, you will either get nothing or get rolled back."