Three hundred thousand telephone calls was just the beginning.

The $8 million campaign for the July 31 Atlanta regional transportation referendum is trying to reach every voter it can who might swing the vote.

Aside from commercials, mailers and forums, the campaign already has dialed up 300,000 metro Atlanta residents to push the message, and expects to do much more.

Considering the obstacles, there’s no telling if the formidable effort will be enough.

In a meeting with The Atlanta Journal-Constitution’s editorial board Thursday and in presentations this week, campaign strategists talked about their tactics and the challenges they face. They also drove home the serious threat they perceive to the region if the referendum doesn’t pass.

Opponents say the tax itself is a threat to the region, and they hope their message will stand up to the proponents’ war chest.

The fight is over a proposed 10-year, 1 percent sales tax to build a list of transportation projects throughout the 10-county region. All 10 counties will vote together and pay the tax together if it passes.

If it does, the tax is expected to raise $7.2 billion overall, with $6.14 billion of that going to a regional list of projects throughout the 10 counties. On the regional list, about half the money would go for mass transit, and about half for roads.

The task of knitting together projects that could satisfy the disparate groups in the 10-county region -- transit passengers and car drivers, suburbanites and urban walkers -- was a tough one. Now, to pass that list, the campaign has some equally tough goals.

Though Democratic voters are traditionally less tax-shy, campaign officials know that they don’t love taxes, either, and their wallets have been battered by the economy. Moreover, any voter who walks into the polls uncertain or uninformed is usually a no vote, campaign officials said. So they’re aiming for just 60 percent of Democrats voting in the referendum.

The campaign hopes to win 35 percent of Republican men who come out to vote in the primary. It’s aiming for 50 percent of Republican women voting that day.

Campaign leaders insist those goals are doable. They think they currently have a razor-thin majority.

Opponents say, no way.

"I can understand them doing everything in their power and imagination to get out there and sell as many people as they can on this ridiculous program," said Harold Bost, a Fayette County resident who has been organizing against the measure for more than a year.  "I’ll be very disappointed if 35 percent of Republican men vote for it. And for them to think that the women are not smart, too? I just can’t buy that story."

The pro-referendum campaign's strategy is to tip the balance by getting unlikely primary voters to come to the polls.

“I happen to be a Republican primary voter,” said Paul Bennecke, one of the campaign’s strategists. “I think I’m an example of what people have to deal with every single day in their commute.”

He detailed his drive on I-75, which leaves him with 30 minutes a day to see his eight-month-old son. In addition, he said, for Republicans defense, public safety and infrastructure are the core functions of government.

Campaign leaders and officials with the Metro Atlanta Chamber say the referendum must pass or the region will stagnate. They say Atlanta is already losing jobs as companies decide traffic congestion makes it too cumbersome to relocate here. They don't see a viable option if it fails.

“We’re losing against states like North Carolina and Texas and other states that have invested in infrastructure,” said Carol Tome, chief financial officer of Home Depot and the Chamber’s chairwoman.

Campaign opponents acknowledge the congestion problem, but say the referendum’s project list won’t address it. Opponents from the right criticize the heavy investment in mass transit, saying it won’t take enough cars off the road to make a dent. Opponents from the left say there’s not enough mass transit.

The Atlanta Regional Commission, the region's official planning agency, is holding "wireside chats" where residents can learn more about the referendum projects. For more information see atlantaregional.com.