The plan to build a mass transit system along Salt Lake Boulevard and bypass Honolulu International Airport appears to be holding together at City Hall — barely.

With a crucial City Council vote looming tomorrow, at least three alternative transit routes also are being floated, including two that were torpedoed earlier.

But there were no clear indications late last week that any plan had gained enough political traction to replace the Salt Lake path that the council tentatively approved Wednesday.

That route — part of a larger segment that would run from Kapolei to Ala Moana Center — was approved as a compromise to win a swing vote from Councilman Romy Cachola and keep the project from stalling.

Opponents of the Salt Lake route have been scrambling since Wednesday to revive a route that goes past Honolulu International Airport or stretch the larger segment's ends east or west.

Phone calls and e-mails flooded into council offices after the Wednesday vote from residents who support the transit route or other links. A few applauded the Salt Lake switch.

On Wednesday, Mayor Mufi Hannemann called tomorrow's vote "perfunctory" and said he was sure the route would not change again. He did not want to be interviewed for this story.

"The mayor still hopes to break ground in 2009, and he is confident he will get a minimum operable segment that meets the federal criteria," a spokesman said.

The segment would become the core of a system that could eventually run from West Kapolei to Manoa and Waikiki.

Voting in favor of the Salt Lake route on Wednesday were Cachola and Councilmen Gary Okino, Todd Apo, Nestor Garcia and Rod Tam. Opponents were Donovan Dela Cruz, Charles Djou, Ann Kobayashi and chairwoman Barbara Marshall.

Okino, who had proposed the Salt Lake route as a compromise, said late last week that he believed it would win final approval tomorrow.

"It was a matter of whether we'll have a project or not — it's political reality," Okino said. "I'm confident it will hold."

Djou said he may introduce an amendment tomorrow that would revive the route Hannemann had originally proposed, from the planned UH-West O'ahu campus to Ala Moana Center via the airport.

"This project is fatally flawed without UH-Manoa and the airport," said Djou, who has opposed the transit plan. "I don't think this project is a good idea, but if we do it, we should at least do it right."

Though there were no solid indications that any council members would switch their votes, Djou said he expected various promises and power plays.

"It's a buffet of political favors right now," he said.

Marshall, who has consistently opposed the entire transit plan, said she would vote against any route — even if that makes it easier for others to approve the worst one.

"There's been an argument made to me that (the project) is going to happen anyway, so you at least ought to support the best route," she said. "It's like saying, 'I don't support the death penalty, but it's OK if you shoot them.' "