A San Francisco Superior Court judge agreed with city elections officials Wednesday that they should not enact a new voter-mandated instant runoff system for the November election even though they will be violating the law.

Forcing the city to use instant runoff voting would endanger the integrity of the vote and therefore should not be done, the judge said.

"The ultimate election outcome would be jeopardized," said Judge James Warren, who issued his ruling from the bench.

San Francisco voters in March 2002 said instant runoff voting should be in place by this fall's election. However, in court documents, the city attorney said that putting the new system in place now would cause a "potential train wreck on Nov. 4."

The election includes races for mayor, district attorney and sheriff.

The Center for Voting and Democracy and the San Francisco Labor Council are part of a coalition promoting instant runoff voting that filed a lawsuit against city elections director John Arntz and the Elections Commission seeking to force the city to comply with the will of the voters. The coalition has not decided whether to appeal Warren's ruling.

Under instant runoff voting, also known as ranked-choice voting, voters would rank their top three candidates in order of preference.

If no candidate had more than 50 percent of the vote in the first round, the candidate with the least support would be eliminated, and the second choice on those ballots would move up to the top with those votes being instantly recounted. This would continue until one candidate had the 50 percent-plus majority.

However, barring a successful appeal, the judge's ruling will keep the city's old runoff system in place. It dictates that if no candidate secures at least 50 percent of the vote in the Nov. 4 election, the two top vote-getters will face off in a one-on-one election in December.

Arntz told the court that it would be impossible to put the new vote- tallying system in place for the November election, given that the hardware and software for a mechanized vote-count has not been certified by the state, and that back-up plans for a partial hand count were rejected by the state authorities.

An alternative plan, for a full manual count by a British firm that specializes in the procedure, has been untested in the United States and would lead to chaos and confusion, Arntz argued, although proponents disagreed. The city attorney also said the proposed alternative would not meet state fair elections requirements.

"We don't want another Florida," said Deputy City Attorney Wayne Snodgrass, who argued the case.

Lowell Finley, attorney for the plaintiffs, said the city was under obligation to enact instant runoff voting. To do otherwise, he said, denies the rights of the electorate and poses "a serious, grave injury."

Warren said Finley's argument was compelling, but in weighing both sides opted to defer to the judgment of the elections director.

Arntz is the sixth director to run the department in as many years. He became acting elections chief in April 2002 after moving up the ranks. He got the job permanently 13 months later, though he is still on probation and serves at the will of the Elections Commission, which is locked in a leadership battle -- ostensibly fueled over differences among the members over instant runoff voting.

Outside the courtroom, after the verdict, Steven Hill of the Center for Voting and Democracy said Arntz and the city's elections department had almost 18 months to get the new system in place and should have succeeded.

"We've seen a lot of fumbling and bumbling going on," he said.

During questioning from the bench, Judge Warren suggested a similar take on the city's efforts to put the new system in place, calling it "at best, bumpy."

Arntz said he had done the best he could but was working with an elections systems vendor who didn't fulfill the promise to have the software and machinery certified on time. Complicating the matter, he said, is the unexpected Oct. 7 state recall election, which has diverted staff resources at the Department of Elections.