The guessing game in the Georgia Senate race is in its final round, as primary voters head to the polls next Tuesday to decide the longest and shortest primary contests of this election cycle.

Wrapped into the equation are three incumbent House Members, two millionaires and the more plausible than once thought prospect that two black candidates could square off on the November ballot.

Republicans are still heavily favored to win the seat of retiring Sen. Zell Miller (D) in November.

For the most part, the intrigue remains highest on the GOP side, where all eyes are focused on whether Rep. Johnny Isakson can win the primary outright and avoid what would likely be a brutal three-week run-up to the Aug. 10 runoff. He faces Rep. Mac Collins and former Godfather’s Pizza CEO Herman Cain on the primary ballot.

To escape a runoff he would have to get more than 50 percent of the vote in the primary, a scenario that GOP strategists say is possible but still not probable at this point.

Among the Democrats running, Rep. Denise Majette is favored to win her party’s nomination, but millionaire businessman Cliff Oxford is spending enough of his personal money on television ads that he could spoil her ability to top the 50 percent mark.

But Isakson has the most riding on his ability to avoid a runoff. He has run and lost two statewide campaigns before, the last being a 1996 runoff to Guy Milner.

Isakson, the first to enter the Senate race shortly after Miller announced his retirement in January 2003, has consistently led in fundraising and the few polls that have been released publicly.

In the past month, no independent or campaign polls have been released.

But Cain and Collins have both worked to portray Isakson as the moderate in a race where the issue of abortion rights continues to play heavily. But as Cain and Collins have set out to out-conservative one another, some groups, such as the Georgia Right to Life Committee, ended up splitting their support between the two men, leaving the primary outcome ever more up in the air.

While Collins has long been viewed as the likely winner of the second runoff spot, that notion has largely faded in recent weeks as his shoestring campaign appears to be running on fumes.

Collins reported raising just $214,000 in the second quarter of the year, compared with Isakson’s $920,000 and Cain’s $752,000.

A high rate of staff turnover has further fueled speculation that Collins’ campaign, which showed $457,000 in the bank as of June 30, has collapsed and at the same time given GOP operatives and insiders more reason to ponder an Isakson/Cain matchup.

When pre-primary fundraising reports were filed last week with the Federal Election Commission, Isakson showed just under $1 million in the bank after pre-buying much of his TV ad time for the final leg of the campaign. Isakson spent a whopping $3.5 million in the three-month period.

On Monday, Isakson announced the support of Eric Johnson (R), the state Senate President Pro Tem, while Cain touted the endorsement of the Albany Herald in south Georgia.

While Isakson’s base lies within the Atlanta business community and much of the GOP establishment, Cain, a motivational speaker, has wowed audiences with his oratory and developed a strong following among conservative activists in the party, and that has translated into pockets of support in rural areas of south Georgia. He is the first black Republican to seek a statewide office since Reconstruction.

“Cain has three beliefs: In God, in himself and in the opportunities this country offers.  Sounds trite? Not when you hear this man say it,” the Herald’s editor and publisher wrote. “Cain is believable. He is an optimist. He evokes confidence. He is engaging and energetic. His straightforward manner is refreshing. … He exudes enthusiasm that is contagious. He instills hope.”

A runoff featuring Cain and Isakson would no doubt be one of the most interesting and dynamic of the cycle.

Although Cain has exceeded all fundraising expectations and therefore not dipped into his personal fortune to finance his campaign, his ability to pour millions into a runoff could wreak havoc for Isakson. At the very least, heavy spending by Cain would leave Isakson battered and broke if he does emerge from the runoff.

Cain also has the backing of the Club for Growth and the group could decide to play a larger role in the runoff, whether through advertising or bundled contributions.

A runoff with Collins, on the other hand, would pit Isakson against a severely underfunded opponent, albeit one who would have the upper hand among social, Christian and so-called “movement” conservatives.

In the past week, Cain and Collins have clashed as they vie to make the runoff. At a debate Sunday Collins routinely attacked Cain’s lack of experience and knowledge.

Until recently, Collins had focused his attacks primarily on Isakson and his votes on abortion rights legislation. But last week Collins went up with a new set of ads taking shots at both Isakson and Cain.

“I am Mac Collins. I approved this message so you’ll know there’s a real difference between Mr. Isakson, the moderate; Mr. Cain’s inexperience; and Mac Collins, the proven conservative,” Collins says in the opening of the 30-second spot.

Cain has already aired a barrage of spots hitting Isakson on taxes and abortion issues. When the three candidates debated Sunday, the affair was largely amiable.

Meanwhile, a Democratic debate Sunday was not as cordial, as Oxford, the free-spending millionaire, took the brunt of the criticism. While Majette is favored to win the primary, the absence of a runoff is not a forgone conclusion with Oxford’s spending already having triggered the so-called “Millionaire’s amendment” of the new campaign financing laws.

Oxford, who made millions from the sale of his technology consulting firm, has also had to contend with baggage from two previous divorces and accusations that he was physically and verbally abusive to one of his ex-wives. The couple has since reconciled and she is supporting his bid.

Oxford called the continued references to his personal life a “cheap shot” during the debate.

In the debate, Majette also highlighted Oxford’s failure to vote in five elections between 1996 and 2000.

Oxford has owned the TV airwaves on the Democratic side and Majette at this point does not look likely to advertise on TV before the primary. She has run radio advertising and focused on running a grassroots campaign.

While it has been estimated that black voters may make up more than 50 percent of the Democratic primary electorate this year, Majette said Monday she is reaching out beyond her base.

“I’m certainly excited about the prospect of the African American community being engaged and coming out to vote in record numbers but as I said we’re traveling across the state reaching out to all the voters,” she said in an interview from Dawson on the second day of her “Earn the Vote” tour across the state. “Because we all share the same priorities. We all have the same values.”

Majette’s pre-primary report showed she raised $317,000 in the second quarter of the year and had $287,000 left in reserve as of June 30. Eleven members of the Congressional Black Caucus have donated to Majette’s Senate campaign.

Oxford, meanwhile, loaned his campaign just less than $1 million in the period and spent most of that total.

Among his few individual contributors were former Gov. Roy Barnes (D), who gave $500, and state House Speaker Terry Coleman (D), who gave $250.

Oxford’s TV commercials have focused largely on his plan to create jobs and the outsourcing of American jobs have been a primary theme of his campaign.

Still, he was unable to nab the state AFL-CIO’s endorsement in June. The labor group backed Majette.