Last month's U.S. Senate race in Mississippi saw GOP incumbent Thad Cochran survive a tea-party assault, aided by the U.S. Chamber – plus thousands of black Democrats lured into the Republican runoff.

In the weeks that followed, political observers wondered if Cochran’s success would have implications here.

Last Tuesday brought the answer. Mississippi indeed sparked ideas in Georgia’s Republican runoff for Senate — just not the ones you might think.

Snubbed by the powerful business group, former Dollar General CEO David Perdue used antipathy toward the U.S. Chamber and its Mississippi adventure to pry apart an alliance of Republican stalwarts and tea partyers that Jack Kingston, the Savannah congressman, was about to ride to victory.

Given his slim 8,529-vote margin, Perdue’s stunning victory over Kingston and Georgia’s GOP establishment won’t lack for parentage. A superior television ad campaign, an effective voter identification operation, a surplus of turnout-boosting contests in north Georgia, and a willingness to open his thick wallet – all factored into the first-time candidate’s win.

But it was the Perdue campaign’s last-minute decision to cast the U.S. Chamber as the villain in the race – and in doing so, raise doubts about Kingston’s opposition to immigration reform – that may have turned the final trick.

“It’s hard to beat a guy that can stroke $3 million checks, has the name ID of the ex-governor and his network, and he’s the legitimate outsider. But Mississippi may have mattered,” said Eric Johnson, a former state Senate leader from Savannah who headed up the Southern Conservatives Fund, an independent committee that supported Kingston’s candidacy.

At first, there was no downside to the U.S. Chamber’s spring-time endorsement of Kingston, a 22-year veteran of the U.S. House and a member of its appropriations committee.

Which came not long after Perdue walked out of an interview with Chamber executives in a fit of temper. We’re told the former Fortune 500 exec was ticked that the business organization wasn’t automatically lining up behind one of its own.

The benefit of U.S. Chamber backing became apparent after Perdue and Kingston, their campaigns broke and exhausted, survived the May 20 primary.

The Chamber stepped in and began airing $2.3 million in TV ads to boost Kingston’s campaign, which allowed the candidate to court Georgia tea party leaders and former rivals such as Karen Handel and Phil Gingrey.

Endorsements from Republican elected officials across the state began piling up on Kingston’s doorsteps. Polls responded accordingly – and the coastal congressman began looking like a sure thing.

Then came June 24 and the Senate runoff in Mississippi. The intervention, part of the Chamber’s national effort to rescue the Republican party from its self-destructive excesses, saved a 36-year Senate veteran but doomed tea party favorite Chris McDaniel.

Julianne Thompson of Atlanta Tea Party Patriots, a former Handel supporter, was the first tea party activist to publicly sign up with Kingston after the primary.

The Chamber’s activity on Cochran’s behalf didn’t shake her own commitment to Kingston, but Thompson knows it angered others in her movement.

“As far as grassroots conservative activists are concerned, there is a distrust for the Chamber of Commerce,” Thompson said. “They seem to have become less about being pro-business and more about being in the middle of political races.

“I think it was a wise move on the Perdue campaign’s part to distance itself from the Chamber. I don’t disagree with them on that,” she said. “I think that David ran more of a tea party-type campaign, and that resonated with the voters at large.”

Bottom line: Four weeks later, when the Georgia GOP runoff for Senate came down to the wire, and Kingston went on TV with accusations that his rival was soft on illegal immigration, the Perdue campaign knew how to respond – and when.

Across Georgia, TV stations have a Friday noon deadline for purchasing weekend air time. Perdue operatives snuck in just under that deadline and plastered three days of television programming favored by the 55-and-older crowd with an unanswered 30-second spot that underlined the U.S. Chamber’s support for immigration reform. The ad declared Kingston “bought and paid for.”

"Kingston's largest backer, who has pumped almost $3 million into Kingston TV ads, is 100 percent openly pro-amnesty. Kingston now owes them big," the Perdue spot pronounced.

A Chamber operative cried “sour grapes,” but the timing of the Perdue assault permitted no televised response.

On Tuesday, as Republicans in metro Atlanta pushed Perdue over the finish line, conservative talk show host Erick Erickson, another Kingston supporter, offered this benediction on Twitter:

"Was able to convince A LOT of people to back candidates I was supporting, but the Chamber of Commerce endorsement of Kingston hurt him badly."

What Mississippi had given, Georgia took away.

We reached out to the Chamber for a post-election discussion of events, but did not hear back. A petulant video attacking Perdue, posted on YouTube before the Tuesday vote, has since disappeared.