You're paying a tax and you don't even know it.

That's the message a high-powered political campaign has begun pounding home to metro Atlanta voters as a July 31 referendum on a sales tax for transportation improvements approaches.

Don't like taxes? We're with you, the campaign says. Yet Atlantans pay a daily price in wasted fuel, earnings and personal time sitting in traffic.

This "congestion tax" can only be curbed with --- you guessed it --- a new sales tax that would raise $7 billion to help ease tie-ups.

Some $8 million worth of commercials, billboards, mailers and telephone calls have just launched their pro-sales tax campaign.

It might be the biggest campaign ever waged for such a ballot measure, according to national experts. And it may need every penny. The voter base is huge. The candidate isn't a charismatic politician; it's a fragmented list of at least 157 transportation projects unlikely to satisfy everyone. Tax-wary opponents are already railing against the plan and polling has indicated it could be a tough sell with many voters.

Advocates' message will be critical if the balance is to be tipped.

Adding to the challenge is the fact that many average voters have never even heard of the referendum. By the time the vote happens, the campaign means for the question to dominate public conversation in metro Atlanta.

"This process . . . has never been tried before, " said Paul Bennecke, one of the strategists leading the campaign. "We're starting from scratch."

The voter

No one has ever tried to unify as many disparate Atlanta counties --- urban and suburban, rich and poor, drivers and mass-transit riders --- to vote as a region to fund anything.

The campaign is boiling down the unprecedented challenge. Out of 2.3 million voters, 350,000 to 400,000 may vote on the July 31 ballot, the campaigners think. The campaign plans to target the 30 percent to 40 percent who are believed to be undecided along with the roughly 35 percent who are leaning toward voting yes.

"If you're a yes, we're going to find you, " Bennecke said.

A poll commissioned by The Atlanta Journal-Constitution last fall found that 71 percent of voters were not familiar with the referendum. Fifty-one percent were leaning toward voting for it, but that was a fragile lead so far out, said pollsters Mason-Dixon Polling and Research. On such a ballot initiative, they reasoned, opponents have the advantage because they just need to make voters uncertain.

When the campaign in favor finds those potential yes voters, they must deliver a message honed for Atlanta. Polls and focus groups have shown, for example, that while regional leaders worry that transportation investment in regions like Charlotte and Dallas is positioning them to take growth from Atlanta, voters aren't concerned about that.

The Atlanta campaign, instead, must concentrate on the toll traffic takes on people's lives and livings. The average driver wastes more than 40 hours a year in Atlanta traffic, and congestion costs the region $2.5 billion a year in wasted time and fuel, surveys indicate.

"Not only have they become inured to [traffic], but they have become inured to the cost, " said Jeff Dickerson, a campaign spokesman. "Somehow we've got to get them to see that's not normal."

The slogan for the referendum: Untie the knot.

In TV ads that have already debuted, traffic congestion takes the shape of a giant cartoon knot of roads clogged with vehicles. A big belching truck evokes Atlantans' loathing of highway truck traffic. The ad says congestion is "killing jobs."

Then in animated commercials, with trains and the Ga. 400 / I-285 signs (a big interchange project on the list) flashing by, the referendum unties the knot. It comes undone, and commuters move more freely.

On cable, where ads can target a more specific audience, future commercials will probably advertise more specific projects. Mailers will list and map the proposed projects.

Another peculiarity of the Atlanta mindset is the intensity of feelings over mass transit. Some people really love it, and others really hate it.

One flier sent to suburban homes --- where roads, not transit, were generally preferred for the referendum --- lists 35 road projects throughout the metro area. There's no mention of the referendum's big investments in MARTA and regional buses. Campaign officials say some of those fliers were sent to Atlanta, too. The ads push people to the website, UntieAtlanta.com, which will soon contain the full list of projects.

The campaign is split into "education" and "advocacy." Right now, the education website, transformmetroatlanta.com, has the full project list.

To craft the messages to the fragmented metro Atlanta voter base, the campaign created a fragmented collection of messengers. Scores of supporters, from property developers to environmentalists, have signed on for the campaign's "speaker's bureau." They are making speeches aimed at educating civic and other groups.

There is as yet no single, high-profile spokesman.

In some regions, a single face with gravitas made a difference. In Denver, now-Gov. John Hickenlooper boarded a light rail train in a television commercial for that region's referendum. Voters swooned.

The two Atlanta commercials so far don't use personalities.

Gov. Nathan Deal has come out squarely in support, braving the fury of tea party members who backed him but mostly oppose the tax. Asked if he would appear in the campaign's ads, Deal told the AJC, "Nobody's asked me yet."

Nothing says that's necessary, said Alan Wulkan, a consultant to transportation campaigns across the country, including Charlotte and Phoenix.

In Atlanta, "you've got some communities who are conservative, white, others that are African American, others Hispanic, you've got the whole spectrum of political groups in the Atlanta region, " Wulkan said. "I think having a single champion would probably be a real challenge."

The campaign's most intense work will occur in the four counties where the most targeted voters are. DeKalb, Fulton, Gwinnett and Cobb counties contain 72 percent of them, Bennecke said.

Some voters are beyond convincing, and the campaign isn't going to try. Those include not only tea partyers who deplore the reliance on mass transit, but also others who believe transit was slighted in the project list.

Tia Shambry, an IT data report writer who commutes from Dunwoody to downtown Atlanta, is undecided. She agrees that traffic is "definitely a problem" and she wants better planning and creative thinking, not ever-wider highways. She is skeptical of expanding transit in the suburbs for fear it will bring crime.

But in the end, the project list will help her make up her mind. She plans to read it on the campaign website "just to know how it will affect the community, " Shambry said.

Sharon Burt, a sales representative who lives in Brookhaven, drives up Ga. 400 every day to Northridge Road. She's seen the "ball of yarn" campaign commercial but still doesn't know how she'll vote.

While she approves of plans to expand MARTA and she could be helped by plans to expand the Ga. 400 / I-285 interchange, no single project will draw her yes vote. "I want to see the plan in its entirety, " Burt said. "If I decide half of the projects I don't agree with or don't make sense or I don't think are going to be a viable solution, I would probably vote no."

The operation

To reach voters, about a dozen campaign staffers have set up shop in spare offices in downtown Atlanta rented at a discount from Cousins Properties. They mirror what they hope the voter base will be: a collection of people from different ends of the political spectrum rallying around what they see as an imperfect but acceptable collection of projects.

In a small room with a handful of campaign staffers, the two black "moderate" Atlanta residents sat on one side of the desk and the two white Republican suburbanites on the other. They all recalled their first meeting, where they sat down and reminisced about all the campaigns or issues where they'd opposed each other. But in this campaign, they share the belief that traffic is not political.

"It transcends traditional political lines, " said Dickerson, a spokesman for the campaign. "It obliterates lines."

They have hired a dozen vendors and consultants to run everything from research to social media. Their plan includes thousands of volunteers and paid workers to make phone calls and canvass door to door.

And $8 million to spend.

"That is a formidable sum, " said Peter Haas, director of the San Jose, Calif.-based Mineta Transportation Institute, who studies transportation votes. "You need to have significant funding behind the campaign to get the message out."

The $8 million campaign for 10 counties would spend as much as Deal raised for his gubernatorial race in all 159 counties, although outside groups spent money as well. The transportation advocacy campaign chest is to be raised from private donations.

A 2008 campaign to pass high-speed rail in California spent $2.5 million, according to that agency. The 2004 Denver campaign spent $3.7 million.

It's hard to draw comparisons because other campaigns haven't been so closely coordinated, said Jason Jordan, director of the Center for Transportation Excellence, which tracks such referenda. But he wouldn't be surprised if the Atlanta effort was the biggest.

The Atlanta campaign's work, ads and spending will become more intense as voting dates near. Absentee voting starts 45 days before election day, some special early voting 21 days before, other early voting a week before, and then election day, July 31.

The opposition is not nearly as well funded or organized, but it's passionate. Opponents are setting up websites and a political action committee and holding meetings.

Field Searcy led a recent meeting in Cobb County. He says the pro-tax campaign may have money on its side but he has the truth on his side --- that the tax won't really help traffic.

Still, Haas said the pro-tax campaign should be able to accomplish its first big task. "One thing we found is it's really important that the community itself needs to sense that transportation is an urgent and pressing problem. I sense that in a place like Atlanta that's not a hard thing to meet."

Some say it might just work: A handful of big-ticket projects, such as the Atlanta Beltline, highway interchanges on I-285, and a rail line to Emory University, each will strike a chord with hundreds of thousands of voters.

But others are skeptical.

Joel McElhannon, a Republican consultant and president of South Public Affairs Consulting LLC, says the campaigners are pros. But they'll need to be: He thinks the Atlanta project list contains too many small projects, and that putting half toward mass transit was too much.

"It doesn't mean it won't pass, but when you combine how complicated this is, with the economic climate and with the fact that a lot of Republican primary voters are turning out who are naturally suspicious of taxes, it's a real uphill climb."

The other races on the July 31 ballot are a mixed bag: For the first time in more than two decades, no contested senatorial or gubernatorial races will bring out voters. Some contested local races, including challengers campaigning against the tax in Cobb County, could swing either way.

About that, Bennecke said, "I'm not concerned at all."

"I happen to live in Cobb County myself, " he said. "I have to commute up I-75 every day. It's a beast. . . . I think we've got a list of projects that really sells itself. I think we've got a great story to tell."

Staff writer Aaron Gould Sheinin contributed to this article.