A new Elway Research poll released Monday shows a 13-point drop in support for Tim Eyman's tolling initiative, I-1125, since last month.

"After gaining ground over the summer, support for I-1125 dropped from 56 percent in September to 43 percent last week," pollster Stuart Elway wrote. "At the same time, opposition grew from 25 percent to 36 percent. The proportion of undecided voters has remained relatively steady all year at around 20 percent."

I-1125 would require the Legislature to approve tolls instead of the state Transportation Commission; ban variable-rate tolls, which charge more during peak driving times, and mandate that tolls only go toward work on the road being tolled.

It also would prevent Sound Transit light rail from running across the Interstate 90 bridge.

Eyman tried to put a positive spin on the poll, noting that the number of people supporting the measure still exceeds those opposed.

"We're pleased that we're still ahead," he said in an email. "As always, it'll boil down to what the undecided voters do."

Sandeep Kaushik, a spokesman for the no campaign, Keep Washington Rolling, said, "I think as voters are digging into the initiative and hearing what both sides have to say about it, they realize it's a bad idea for Washington state."

The poll surveyed 407 voters statewide on Oct. 19-20. It has a margin of error of plus or minus 5 percentage points.

Eyman says the initiative would make lawmakers more accountable for raising and spending billions of dollars in tolls, and would make tolling fairer by banning variable-rate tolls that he says hit the state's poorest residents the hardest.

Opponents say it would undermine the state's ability to finance large transportation projects, including the Highway 520 floating bridge and a new Interstate 5 span over the Columbia River.

Keep Washington Rolling has raised more than $2.2 million, including $960,000 from Microsoft and its employees, including CEO Steve Ballmer. The campaign is running a statewide television ad campaign.

State campaign finance reports filed last week show the no campaign with more than $900,000 in the bank. Eyman's campaign showed a negative balance once debts were taken into account.

Eyman's campaign has raised $1.35 million, with more than $1 million of that from Bellevue developer Kemper Freeman.