Used in San Francisco, the system eliminates primary contests in most cases, and lets voters rank their selections.
Voters in Minneapolis tossed out years of tradition by adopting a new voting system for local elections, a historic change that supporters said would increase voter participation.
With more than 93 percent of the precincts reporting, city voters approved by nearly a 2-to-1 ratio a charter amendment for instant-runoff voting, a system used in San Francisco and two other U.S. cities.
"It clearly shows that Minneapolis is ready to take the next step toward democracy," said Jeanne Massey, lead coordinator for the Minneapolis Better Ballot Campaign.
The election system eliminates primary elections for most municipal contests and allows voters to rank their choices for office, instead of choosing a single candidate.
In some elections, voters' second or third choices could help push candidates to victory.
The new system would affect elections for mayor, City Council, Park and Recreation Board, Library Board and Board of Estimate and Taxation. It could be used as early as 2009.
Local supporters say the system eliminates costly primaries in those races, and focuses on more issue-oriented campaigning. Opponents said it allows fringe candidates an enormous influence in elections.
"This result is indicative of a totally disenfranchised and alienated electorate," said Andy Cilek, head of the Minnesota Voters Alliance, whose group opposed the measure.
City officials have estimated that it would cost Minneapolis about $1.8 million to implement the system. The voting process was endorsed by Mayor R.T. Rybak and a majority of the City Council.
Rybak said voter support Tuesday resulted from "a tremendous grass-roots effort" showing "this city will accept change, if presented well."