BURLINGTON, Vt. -- Runoff elections are traditionally cumbersome processes, taking weeks and sometimes months to determine a winner. On Tuesday, Burlington will do it all instantly.

The results for the first election and whatever runoffs are needed to settle a five-way race for mayor will be known soon after poll closing.

That's because voters, for the first time in a mayoral election in the United States, will vote Tuesday not only for their top choice, but also for their second, third and fourth choices through an innovation known as instant runoff voting.

Voters will be handed a ballot listing the five candidates, three of them representing major parties, with columns indicating first through fifth choices. If none of the five gets 50 percent of the vote on the first round, the candidate with the lowest vote total would be eliminated. The second choice of voters who made that candidate their initial top choice then would count.

"As soon as somebody gets to 50 percent, it stops," said Jo LaMarche, the city's election director.

Advocates have been promoting the idea of instant runoff voting, also known as ranked-choice voting, as a way of boosting voter turnout, encouraging more people to run for public office while eliminating the notion that a third-party candidate might be a spoiler.

"Nationally, people are catching on to how IRV can open up our politics," said Ryan O'Donnell, communications director of FairVote and the Center for Voting and Democracy. "It's a reform that produces majority winners, encourages candidates to reach out to more voters, and eliminates the 'spoiler' problem."

Burlington will not be the first community in the country to use a form of instant runoff. San Francisco has elected members of its board of supervisors using the system and the city of Ferndale, Mich., also is scheduled to use it. It will be the first to elect its chief executive officer with the system, though.

A number of other counties, cities, and towns also have shown interest, according to FairVote, including San Diego, Oakland, Davis and Berkeley in California. Bills are pending in at least 15 states to implement instant runoffs at local levels or statewide. The state of Washington last year gave a number of mid-sized cities authority to conduct instant runoff voting, although none has so far used it.

LaMarche said she's heard a lot of interest as well, fielding calls from South Carolina, Anchorage, Alaska, and communities in northern California. "A lot of people are just waiting to see how this works with Burlington," she said.

An academic who has studied voting systems said Burlington deserved the attention, despite its relatively small size. "I think it's significant because it's going to put Burlington on the cutting edge of this kind of election reform," said Doug Amy, professor of politics at Mount Holyoke College and author of "Behind the Ballot Box: A Citizen's Guide to Voting Systems."

He said the outcome of the 2000 presidential election likely would have been different if Florida had used instant runoff voting. Amy predicted that votes that went to Ralph Nader ultimately probably would have gone to Al Gore if there had been an instant runoff, giving the former vice president victory in Florida and ultimately the presidency.

"I think that really brought that problem to national attention," he said. "It allows people to vote for any candidate they want and they don't have to worry about electing someone they least want."

Not everyone is enthusiastic about the reform, though. Some election administrators around the country worry that because the system is somewhat more complicated than traditional plurality voting, fewer people will show up at the polls. There's also concern that some ranked choices might not get counted in second and third rounds, a problem that initially bedeviled the system in San Francisco.

Doug Lewis, director of the Election Center, which represents elections administrators nationally, said those all are concerns he and his colleagues have heard about instant runoffs. But he can't say whether they're valid.

"Most of my folks don't have the time or inclination (to investigate) because we're so busy," he said. "Until you work with it enough and find out, it would be difficult to find out."

LaMarche believes Burlington voters will not see much unusual. The city is using the same optical scanning machines and ballots that it's used in the past. The only difference is that there are extra ovals after each mayoral candidate's name for second, third, fourth and fifth choices.

The city clerk's office conducted some voter training in January to try to get voters interested and educated. There also have been mailings to all voters with graphics and text explaining how the system works.

Candidates even have tried to take advantage of the new system. Progressive Party candidate Bob Kiss' signs promote him as the "first choice for mayor." Republican Kevin Curley has told his supporters that he endorses Kiss as a second choice. Democrat Hinda Miller has declined to endorse a second choice, arguing she's confident she'll win in the first round.