A majority of voters in Marin and Sonoma counties said they would oppose the repeal of Measure Q, the sales tax measure funding the Sonoma-Marin Area Rail Transit project, according to poll results released today by the North Bay Leadership Council.

Fifty-eight percent of voters in Sonoma and Marin counties would oppose the repeal, based on a survey of  of 501 registered voters conducted by San Francisco-based consulting firm Dresner Wickers Barber Sanders. The firm conducted the poll between Oct. 27 and 30. The margin of error was 4.37 percent.

Thirty-two percent of responders said that they would support a repeal, and 10 percent said they were not sure or refused to respond.

Cynthia Murray, president and chief executive of the leadership council, said in a statement that the results reflected strong support for the SMART project and the 900 jobs the transit agency expects to create by the end of the year.

"We hope that these compelling poll results lead the anti-SMART group to drop its efforts to stop the train," she said. "The train opponents have already cost Marin and Sonoma taxpayers millions of dollars in bond sale penalties. Now they want to make taxpayers pay even more for an unnecessary, expensive do-over election that voters already decided in 2008."

Yet Clay Mitchell, co-chair of the Repeal SMART group, said that the poll results reflected an erosion of voter support for tax measure.

Nearly 70 percent of voters chose to approve Measure Q in 2008, including Mr. Mitchell. Yet as costs have risen and the initial scope has decreased, the co-chair said that the poll reflected the greater numbers of voters who felt that they would not support SMART in its present approach.

"Something has changed pretty substantially, and we're a part of that," he said.

The group is currently working to collect the 15,000 signatures necessary in both counties to bring a repeal measure to the ballot.

After seeing the results today, SMART General Manager Farhad Mansourian said they reflected continuing support for the project.

"All of the reasons voters approved this in 2008 are the same," he said, including creating an alternative to traveling on Highway 101 and providing a more environmentally friendly option to commuters.

When asked about the criticism that SMART's initial operating segment -- between Santa Rosa and San Rafael -- is shorter than the Cloverdale-to-Larkspur span voters faced in 2008, Mr. Mansourian said that residents knew they would one day have a full system.

"My mandate from the SMART board is Cloverdale to Larkspur," he said. "They hired me to do a full project."

SMART is in final negotiations for the project construction contractor. The goal is to present that company for board approval next month or in January.

The first segment of the commuter rail line is planned for completion in late 2014.