A state House proposal to implement “instant runoff” voting in county races could add at least $750,000 to Hono­lulu’s election costs if it survives conference committee next week.

House Bill 638 would require that all county races statewide without primary elections use a second-choice voting system similar to ones used in other cities.

That would eliminate November runoff elections on Oahu and the Big Island, deciding election contests in those counties in September.

In instant runoff voting elections, if no candidate has a majority of the votes cast, candidates at the bottom of the standings are eliminated, and their supporters’ votes are redistributed to their second-choice candidates, then third- or fourth-choice, until one candidate garners more than 50 percent of the vote.

Nikki Love, executive director of good-government group Common Cause Hawaii, said the instant runoff makes election outcomes more representative of the voters’ intent.

“Instant runoff voting lets voters accurately express their preferences, allows many candidates to run without fear of distorting the outcome and helps prevent the ‘spoiler’ effect,” she said.

Two recent examples of what Love calls “spoiler elections” include the special-election victories last year of former U.S. Rep. Charles Djou and Hono­lulu City Councilman Tom Berg. Djou won with 40 percent of the vote in a field of 14 candidates. Berg, also against 13 others, won with just 2,326 of the 12,559 ballots cast.

Berg, a local tea party activist, led the City Council in drafting a resolution opposing the bill, which passed with unanimous support earlier this week.

“It’s a nonreform masquerading as a reform,” said Berg. “Minority representation will be harder to achieve. And if anything has been proven in recent months, it’s that Dem­o­crats alone cannot run Hawaii properly.”

Honolulu Elections Administrator Glen Taka­ha­shi said the bill also would change how regular mayoral and City Council races are decided, as well as those on the Big Island. Under current rules, if no candidate receives a majority of votes in the September “special nonpartisan” election, the top two vote-getters go to a November runoff.

It would not affect county elections in Maui and Kauai counties, where the top two candidates automatically go to the November ballot.

Preliminary estimates for upgrading the city’s voting machines and ballots are pegged at $200,000, with $250,000 necessary for testing and certifying the new system and $300,000 for voter education materials.

The bill does not include an appropriation, and City Council members said they expected the cost of the upgrades to be placed on the city.