MARTA inched closer to a history-making expansion on Tuesday, but not to the extent many had hoped.

Clayton County commissioners, in a 3-2 vote, opted to let residents decide in a Nov. 4 referendum whether to fund MARTA service within the county by paying a half-penny sales tax. The half-penny sales tax is expected to generate about $25 million a year. MARTA officials have said that’s enough to fund robust bus service, but not enough to fund an expansion of rail.

It’s unclear whether the MARTA board — which votes Wednesday — will approve Clayton’s participation in the transit system without the same full-penny sales tax support that Fulton, DeKalb and the city of Atlanta contribute.

MARTA Board Chairman Robbie Ashe told commissioners, “I do not believe majority support for such an approach exists on our board or among our existing jurisdictions.”

A sales tax of 1 cent on the dollar would have generated about $49 million a year — enough to bankroll a rail expansion as well as buses, and enough to allow the county two representatives on the MARTA board. MARTA had also agreed to set aside any money left over from the full penny sales tax to provide for a future high-capacity transit expansion in Clayton.

But commissioners who rejected that idea said they feared that a 1-cent sales tax hike might stifle business. They also were concerned that a rail expansion could take longer than the 8-10 years and cost more than the $270 million to $350 million that MARTA officials had estimated.

If Clayton voters give a thumbs-up to bus service, it would be the first expansion of MARTA beyond the confines of DeKalb and Fulton counties since the agency began operating 42 years ago.

Several hundred Clayton residents packed the commission meeting room Tuesday night and spilled into the halls. Shirley Whitmire of Riverdale was one of them, and she supported a full penny sales tax.

“We just need this to happen,” Whitmire said. “This county is decades behind.”

Roberta Abdul-Salaam, who founded Friends of Clayton Transit, chastised the commission for failing to consider the 1-cent tax.

“We don’t want just a bus thrown up here,” Abdul-Salaam said. “We want a quality, first-class transportation system.”

At one point, a transit advocate who addressed the commission asked everyone who felt similarly to stand. About 90 percent of the room was on its feet. But a few attendees harbored concerns about bringing transit to Clayton.

One was homeowner Kathryn Brown, who lives in an unincorporated area near Jonesboro.

“Clayton has a lot of lower-income people; I’m all for helping my people,” said Brown. But she said she’s concerned that any revival of public transit could bring “an element of crime” to the county.

County leaders had been wrestling with whether to put the issue on the ballot since March, when state legislation was passed to enable a sales tax increase. Commissioners Sonna Singleton, Michael Edmondson and Gail Hambrick voted for the half-measure after expressing reservations about the level of service MARTA could provide and how long it might take to get a rail line.

That question grew more sticky last week after Norfolk Southern, which owns the freight rail where a commuter rail between East Point and Jonesboro is envisioned, sent a letter to MARTA saying its $270 million cost estimate and 8-to-10-year timeline for delivering rail were probably “dramatically understated.”

The company has not performed any analysis to determine whether passenger service on its line was feasible, the letter said.

“MARTA can’t deliver rail in the foreseeable future,” Edmondson said. “I think it would be irresponsible to tax my taxpayers for something I can’t provide, for something MARTA can’t provide.”

Multiple leaders across the state have backed bringing MARTA service to Clayton County, including Atlanta Mayor Kasim Reed and Gov. Nathan Deal.

MARTA CEO Keith Parker said the commission’s approval is the second step in a five-step process. The MARTA board still has to approve the contract, followed by Clayton voters, and finally two of three surrounding jurisdictions (Atlanta, Fulton and DeKalb) before a deal can be finalized.

Economist Bruce Seaman said MARTA could be just what Clayton needs to differentiate itself from other metro counties and spur economic development.

“It’s moving past the clear sense of most metro residents that something has to be done on the transportation front,” said Seaman, a professor at Georgia State University. “(Clayton) could be in the forefront in the longer-term expansion of MARTA.”