The proposed regional sales tax for transportation and other purposes is losing ground less than a month before its fate will be decided by voters in a July 31 referendum.

Only 38 percent of voters sampled in the 10-county metro Atlanta region support the new sales tax, while 49 percent oppose it, according to a poll last week by Rosetta Stone Communications for WSB-TV. That’s a big drop from 42 percent support versus 45 percent opposed in a late May survey by the polling firm.

Only Fulton and DeKalb now provide significant support with a combined 50 percent in favor and 32 percent opposed to the proposal that is estimated to raise more than $6 billion for transportation projects, airports, parks, sidewalks and other amenities, while generating economic development.

The TSPLOST is in serious trouble in the other eight counties — Cobb, Cherokee, Clayton, Douglas, Fayette, Gwinnett, Henry and Rockdale. In this doughnut around Atlanta, nearly two-thirds of the voters — 61 percent — oppose the tax while only 29 percent favor it. The lowest level of support is in north Fulton, Cobb and Cherokee counties, according to pollster John Garst. If supporters are to improve their chances, they must focus on heavily populated south DeKalb and Clayton counties, but as the pollster pointed out, there’s a short window of opportunity to try to reverse the numbers.

Despite the heavy advertising and strong support from the business and political communities, opponents have made headway since several groups decided to form a coalition working against the TSPLOST, officially known as the Transportation Investment Act referendum. The Georgia Taxpayers Alliance is spearheading “a grassroots campaign” to defeat the proposal.

Even more troublesome for the proponents, the respected Georgia Public Policy Foundation, whose trustees and advisory board are dominated by business executives, has given the TSPLOST a bad review. In analyzing the plan, GPPF Vice President Benita Dodd wrote that while there are some good transportation projects in the proposal, “others won’t move the needle toward mobility while still others are massive boondoggles that will put this state at a disadvantage for decades to come.”

“The prime folly, of course, is metro Atlanta’s list,” she asserted, pointing out that “52 percent of the $6.14 billion funding goes to transit in a region with 5 percent transit use. It includes a push for fixed-guideway transit instead of more flexible bus rapid transit options that could move with population demographics, plus it would commit the region to wasteful spending on questionable projects for long past the 10-year sales tax.”

In Denver, where voters approved a 0.4 percent sales tax for a 12-year regional transit plan in 2004, Dodd reported, “officials are back this year seeking a doubling of the tax and delaying the project completion date.” Other liabilities in her view include the use of a sales tax for the funding and the proponents focusing their “education” efforts on “economic development, jobs and public safety” — instead of “promising that Georgians and freight will be able to travel from Point A to Point B as quickly, efficiently and cost-effectively as possible.”

With opposition coming from across the political spectrum, ranging from the tea party on the right to environmentalists on the left, the TSPLOST is facing a steep uphill battle and likely defeat at the polls July 31.