Charges of Chinese influence-buying in the 1996 U.S. presidential campaign caused a political storm in Washington that has yet to fully abate. By some measures, however, that episode pales by comparison to American political interference in Serbia, locus of a $77 million U.S. effort to do with ballots what NATO bombs could not--get rid of Yugoslav President Slobodan Milosevic.

In the run-up to national elections on Sept. 24, U.S. aid officials and contractors are working to strengthen Serbia's famously fractured democratic opposition. They have helped train its organizers, equipped their offices with computers and fax machines and provided opposition parties with sophisticated voter surveys compiled by the same New York firm that conducts polls for President Clinton.

More generally, they have sought to foster what one aid consultant calls "democracy with a small 'd'," funneling support to student groups, labor unions, independent media outlets, even Serbian heavy metal bands that stage street concerts as part of a voter registration drive called "Rock the Vote."

With Milosevic running well behind in the polls--the latest surveys give his main opponent, Belgrade lawyer Vojislav Kostunica, a 16-point lead--administration officials are mulling a variety of possible outcomes, from capitulation by Milosevic (considered a long shot) to massive electoral fraud (probably the safest bet). Either way, the election is shaping up as the most important test for U.S. policy in the Balkans since the 1998-1999 Kosovo crisis, which led to Milosevic's indictment as a war criminal and triggered the American-led campaign to drive him from power.

"For the first time over the last year, we've seen the emergence of a real democratic opposition," said a senior State Department official. "These elections are a way station on that process."

There is nothing secret or even particularly unusual about the U.S. democracy-building program in Serbia, which is closely coordinated with European allies and is similar to previous campaigns in pre-democratic Chile, South Africa and Eastern Europe, among other places. U.S. officials say they are careful in such situations to focus their energy on building broad-based democratic institutions rather than backing individual parties or candidates, as the Chinese were accused of doing here in 1996.

"There's a specific sensitivity because people assume we pick candidates," the State Department official said. "Our efforts don't do that. We just make sure there's an architecture for a fair election."

But in Serbia, it's a very fine line, in part because the stakes are so high.

U.S. officials dealt with Milosevic as a negotiating partner, albeit reluctantly, during the mid-1990s. But the Kosovo crisis persuaded them that peace cannot prevail in the Balkans as long as he remains in power. They are particularly concerned about his designs on Montenegro, Serbia's smaller partner in the Yugoslav federation, whose pro-Western president, Milo Djukanovic, accused Milosevic in an interview earlier this month of trying to drum up a "pretext for military intervention" in his tiny republic.

Underscoring worries about Serbia and Montenegro, the Pentagon yesterday began a global shift of forces to bolster the U.S. military presence in the Balkans. A carrier battle group led by the USS Abraham Lincoln left Thai waters ahead of schedule and headed toward the Persian Gulf, which will free up another carrier group, led by the USS George Washington, for movement to the Adriatic Sea, Defense Department officials said.

Dismissing Serbia's charges of unwarranted interference in its internal affairs, U.S. officials say they are seeking only to level the playing field in a country whose authoritarian leader thinks nothing of shutting down critical media outlets or tossing opponents in jail.

Fostering democracy in such conditions is ticklish. Milosevic routinely cites American meddling to justify his crackdown on opposition movements and media. According to a senior U.S. official, Serbian police recently arrested and tortured an opposition member after intercepting an e-mail sent to him from the U.S. Agency for International Development (USAID), which, along with the Washington-based National Endowment for Democracy (NED), is one of the major conduits for American aid to the opposition.

Mindful of such risks, the endowment recently stopped posting details of its Serbian program on its Web site. In a similar vein, a NED official smiled apologetically as he acknowledged that while information on grant recipients in Serbia is a matter of public record, he could not release such data without a formal request under the Freedom of Information Act--a process that would extend long past Sept. 24.

Because Americans no longer are permitted to work in Serbia, and U.S. officials are afraid of compromising Serbs who receive their help, aid recipients typically travel to Hungary and other neighboring countries for training, strategy sessions and infusions of cash. Some of the American help also takes the form of humanitarian aid to opposition-led local governments.

There are signs that the American effort has generated something of a backlash. Kostunica, the front-runner, makes a point of telling audiences that he accepts no Western aid. Pro-Milosevic posters show a picture of another leading opposition figure--former deputy prime minister Vuk Draskovic--kissing the hand of Secretary of State Madeleine K. Albright.

Partly for that reason, some analysts accuse the administration of placing too much emphasis on opposition parties and the election rather than on building broad-based movements, such as student organizations, with a long-term commitment to civil society and democratic rule.

"In the last year, the administration has focused clearly, at long last, on the notion that Milosevic is part of the problem, not part of the solution," said a former U.S. diplomat with long experience in the Balkans. "The question is whether they've done a good job of it. Have they put us on a path that's going to lead to success? Well, they've put us on a path to elections . . . that will almost certainly lead to Milosevic's reelection in unfree and unfair conditions. And where will we be then?"

State Department officials acknowledge, as one put it, that "a democratic Serbia is more than just an election." But they also suggest that if Milosevic resorts to massive fraud, it might not be such a bad thing.

"If he steals these elections, he'll be further de-legitimized in the eyes of the Serbian people and the international community and that makes his hold on power more tenuous," said James C. O'Brien, special adviser to the president and secretary of state for democracy in the Balkans.

The pro-democracy campaign did not begin in earnest until the end of last year's NATO air campaign to drive Serbian forces from Kosovo. It has since grown rapidly, from an authorized $10.7 million last year to $25 million this year; the administration has requested $41.5 million for the next fiscal year beginning Oct. 1, for a total of $77.2 million over three years.

The largest share of that money goes toward "civil society" programs, such as those that support independent media, with no direct connection to specific parties or elections. Nevertheless, the administration has associated itself closely with leading Serbian opposition figures such as Zoran Djindjic, president of the Democratic Party in Serbia, who was part of a delegation that received a warm reception in Washington last November.

In a similar vein, USAID this year will spend $3.8 billion on "political process" programs, including "technical assistance" to political parties, get-out-the-vote campaigns and efforts to help opposition parties "develop an economic reform . . . agenda for use in election campaigns," according to an agency fact sheet.

Much of the assistance is channeled through nongovernmental organizations such as the National Democratic Institute for International Affairs, a Washington-based group that among other things has coordinated extensive public opinion surveys in Serbia by Penn, Schoen & Berland Associates, Inc., Clinton's polling firm.

Such surveys can benefit opposition candidates seeking to plot campaign strategy. But Kenneth D. Wollack, the group's president, says the organization is careful to make all the poll results public so that it cannot be accused of backing one candidate against another.

"We try not to inject ourselves into a campaign," he said, adding that the group has, for the same reason, suspended "material assistance" to political parties in the run-up to the election. "We're not in a campaign mode," Wollack said. "We look at our work on a much longer-term basis."

Staff writer Thomas E. Ricks contributed to this report.