Days before Georgia lawmakers convene under the Gold Dome for the 2016 session, MARTA CEO Keith Parker stressed to key leaders the need to significantly expand metro Atlanta’s existing public transit system.

Listening to Parker’s pitch Thursday were several members of the General Assembly, who will soon decide whether to allow a referendum on a half-percent sales tax in Fulton and DeKalb counties to fund an expansion.

If the proposed referendum is approved, and if voters then give the OK on November ballots, metro Atlanta commuters could be looking at a radically different transit system in the future. MARTA officials estimate the money such a tax would generate through the year 2057 would be about $4 billion — enough when coupled with federal grants to effectively double the size of the existing transit system.

The proceeds could fund new heavy rail service north along Ga. 400 to Windward Parkway in Alpharetta and east along I-20 to the Mall at Stonecrest in Lithonia, as well as a light rail line connecting Lindbergh Center Station with Avondale Station through the busy Emory-CDC corridor.

MARTA officials have also said there might be enough money left over to help expand the Atlanta Streetcar system or fund some other type of transit expansion in South Fulton.

“We need some help,” Parker said. “You can do a million things to make yourself more efficient. But you cannot squeeze $8 to $10 billion worth of new projects out of just efficiency alone. We are going to need some new revenues.”

For those reading the political tea leaves, there have been hopeful signs that MARTA’s proposal has a shot. One of the most powerful leaders at the Capitol, House Speaker David Ralston, said at a pre-session press conference Thursday that an expansion of MARTA makes sense, but that he wants the solution to come from the Fulton and DeKalb delegations.

“I have been clear that I think we do need to do acknowledge that transit has a future in our state transportation policy,” said Ralston, R-Blue Ridge. “Now, the specifics … I think we’re going to have to engage with local leaders and see what their vision may be. I’m going to lean very heavily on their input.”

House Minority Leader Stacey Abrams characterized support for MARTA’s plan as a “continuation” of the bargain that Democrats struck with Republicans last year to earn Democratic support for passage of House Bill 170, the $1 billion-per-year transportation tax that took effect in July.

Parker has said that since taking over the ailing transit agency in late 2012, his main priority was to get MARTA’s financial house in order before seeking more money from state or local taxpayers. But on Thursday, he said MARTA has posted three back-to-back years of budget surpluses and has $200 million in reserves.

Ridership increased from 129 million to 136 million passengers rides between the last fiscal year that ended June 30 and the fiscal year prior. And on-time performance for buses and trains in 2015 was a near perfect 96 percent.

Now is the time to start building on that success, Parker said, aiming his comments specifically at the Legislature and Gov. Nathan Deal.

Several state lawmakers from Fulton and DeKalb were among the crowd. Sen. Elena Parent, D-Atlanta; and Representatives Roger Bruce, D-Atlanta; Taylor Bennett, D-Brookhaven; and Tom Taylor, R-Dunwoody, all said they support MARTA’s proposal.

“I’m optimistic,” said Taylor, who chairs the legislative oversight committee on MARTA. “(MARTA) is the backbone of economic development here. I think there’s a lot of momentum behind it.”

Others like Beth Beskin, R-Atlanta, were withholding judgment until hearing more from constituents.

“I don’t think most people really even understand that it’s coming up for a vote,” Beskin said. “There is going to need to be a lot of education on this.”

Transit supporters may still have an uphill battle if they want to squeeze more tax money from parts of North Fulton, South Fulton and South DeKalb that have been paying for MARTA for decades with little or no service in return, said Rep. Chuck Martin, R-Alpharetta, who chairs the Fulton County delegation.

Martin said the proposed expansions would still take a decade or longer to build. And he wants to see more demand studies that indicate how many people would use the new transit lines before he would consider supporting a long-term tax increase.

“I’m looking for a transportation solution for a year or 18 months from now,” Martin said. “And I think that’s more an express bus system or a high occupancy toll lanes.”