LAWRENCEVILLE, Ga. — Backers of Gwinnett County’s MARTA referendum are worried the measure will fail based on early voting.  Older white voters have turned out overwhelmingly in early voting, according to a Georgia Votes analysis. 

Through Wednesday, 77 percent of Gwinnett’s early voters have been over age 55; and 62 percent have been white. Backers of the MARTA initiative say the transit plan is probably doomed if younger voters don’t vote Tuesday.

"If you look at the demographics of who voted," said Brian Robinson, a spokesman for Go Gwinnett, "you would assume that there’s a slight ‘no’ advantage right now."

Robinson is backing the Gwinnett referendum, which would OK a one-cent sales tax to expand MARTA into Gwinnett County.  When we visited an early voting site Friday, most of the voters we saw had a little age on them.  Friday was the final day of early voting.

"A lot of these older white voters... in the polling, they’re the least likely to be supportive. We know that," Robinson said. 

New taxes for transit aren’t always an easy sell.  Gwinnett overwhelmingly rejected MARTA expansion in 1990.  In 2012, the Atlanta region likewise rejected a penny sales tax for transportation called a TSPLOST 63 to 37 percent.

Gwinnett has plenty of young, nonwhite voters who haven’t yet voted.  Although only 38 percent of early voters have been nonwhite, Gwinnett County’s active voter population is somewhere between 47 and 58 percent nonwhite according to county data.  

"If we have a massive turnout, this is going to win handily. A big turnout is good because we know most people in the county support this," Robinson said.

Massive turnouts are not typical in special elections like this one. The best news for MARTA backers at this point is the weather – which is partly cloudy and mild for Tuesday's referendum.

RELATED: Many in Gwinnett County still undecided about MARTA referendum

RELATED: Older white voters dominate Gwinnett's MARTA balloting

RELATED: MARTA expansion vote in Gwinnett County: Here's what you need to know

RELATED: A breakdown of Gwinnett County's upcoming MARTA vote

RELATED: Do Gwinnett County residents want MARTA? The jury’s still out