Armed with a poll that shows Eastside voters on their side, an alliance of urban neighborhood groups, city council members, the mayor, and Seattle’s full legislative delegation from the 43rd District stood abreast today to reject the state's plans for rebuilding the 520 bridge. In December, a legislative workgroup, comprising mostly out-of-Seattle interests, had recommended a 520 bridge that used six lanes for cars, unloaded more traffic into Montlake, built a second Montlake drawbridge, stood 30 feet above the water all the way across lake Washington, included an exit ramp next to the Arboretum, and failed to connect buses to the soon-to-be-built light rail station next to Husky Stadium.

“On the Seattle side, there is no more room for more cars,” said Fran Conley, ringleader of the Coalition for a Sustainable 520. “The current design may bring people more quickly across the bridge, but then they would be stuck in gridlock.” (Past reporting on the problems with this arrangement is here and here.)

Near freeway ramps hissing with traffic in Montlake, coalition members said they want to secure the two new bridge lanes for light rail and buses, kill plans for an Arboretum onramp, and shorten the bridge's height. Some spoke of connecting the transit on the bridge with the light-rail line that will stop across the Montlake bridge.

• Ed Murray, Nick Licata, Mike McGinn, and a woman in blue.

The unity suggests an overdue shift in Seattle’s transportation debate, which has been been an arena of discord among each strata of government, and confined largely to discussion about replacing the viaduct. “I want to applaud the mayor for getting involved,” said House Speaker Frank Chopp. “The previous mayor … was not involved in finding a reasonable alternative.” He added, “The mayor and the council stand united in opposing the current design.”

But closer examination reveals fractures in agreement and strategy among the mayor, council, and legislators; while it’s easy for Seattle to reject the the idea of a 1960s-inspired freeway, it’s harder to agree on what, exactly, could replace it and how to stop the state before it’s too late.

Over the weekend, State Senator Rodney Tom (who represents Medina, where the 520 bridge hits land across the lake) told seattlepi.com that “We're not going back” on the current design. This touches on the most pressing challenge for the new group: If the state begins construction on the Bellevue and Medina side—for a bridge that is supposed to be complete by 2014—Seattle could be locked into accommodating that bridge, making Seattle's potential designs moot.

“If you begin construction on one side, I don’t know what leverage we would have on the legislature,” State Senator Ed Murray said.

Asked if all of the members at the press conference agreed that construction couldn't begin until designs were cemented for the west side, everyone nodded yes. But that’s not exactly true. In a letter to the governor and the chairs of both the state senate and state house Transportation Committee last Thursday, the council asked for support making sure that Seattle-side bridge plans “will not be compromised by advancing the work on the Eastside and the crosslake bridge of the corridor.”

In other words, the council says construction can begin while others in the group say it can't.

“The council has sidestepped that issue to avoid a confrontation with the legislature and the governor,” said City Council Member Nick Licata, who didn’t sign the council's letter.

Fellow City Council Member Mike O’Brien agreed: “There is some timidity in asking what we want in the face of those relationships.” Is the council even united on this position? “If you asked nine of us, you wouldn’t get nine answers there,” O’Brien said.

More after the jump.

State lawmakers reveal disharmony, too. “Two bills passed in the last two years got us into this mess,” said Murray, referring to state legislation authorizing the 520 rebuild. When asked, Murray said he voted against the bill—Chopp and Rep. Jamie Pedersen voted for it.

More pressing than rehashing past disagreements, Licata says, “The trick is to convince the Eastside legislators that high-capacity transit on the bridge will be supported by their constituency."

To that end, the group revealed a poll showing support for the coalition's vision on both sides of the lake. Conducted one week ago by ConstituentDynamics, the survey asked, "How should the new lanes be used?” Sixty-nine percent of people living in Seattle and the Eastside chose “light rail/bus,” and Eastside voters actually supported the transit option slightly more.

But the next hurdle is on this side of the bridge. The leaders of the new coalition now must press beyond detesting the backward, anti-transit bridge approved by the state; they have to figure out what plan they want and how to block the state from steamrolling the city. "The dynamics of no are easier to articulate than the dynamics of yes,” said Licata. Moreover, while Seattle has noble visions of integrating transit, it’s unclear what they can achieve given the $4.65 billion spending cap imposed by the state (which holds the purse strings on state highway projects) or, if they want to spend more on transit, where that additional money would come from.

But it’s something they will need to decide soon. “We are not talking about years—we are talking about weeks or months,” said Murray.