No one, not even the candidates, expected Georgia would see the hottest Senate contest of ’08. This Deep South state, which has not elected a Democrat in a major contest for almost a decade, was thought to have gone so reliably red that Democratic Senatorial Campaign Committee chair Chuck Schumer struggled to recruit a challenger for GOP Senator Saxby Chambliss. In March, Schumer talked a former state legislator who had run a losing campaign for lieutenant governor into making what even Democratic loyalists saw as “a mercy run.”

But a funny thing happened on the way to November: Jim Martin, a former legal-aid lawyer who had made expanding access to healthcare his Statehouse priority, rejected the apologetic stances usually adopted by Southern Democrats. Martin beat a primary foe who bragged about voting for George W. Bush, and then he ran a fall campaign that highlighted his commitment to bring troops home from Iraq, invest in healthcare and education, and, above all, “protect hard-working Americans from politically powerful special interests like credit card companies, insurance companies, banks and oil companies.” Instead of distancing himself from his party’s national ticket–a standard Southern Democratic practice in recent years–Martin embraced Barack Obama, whose campaign was making more of a play for the state than any Democratic presidential contender since Bill Clinton.

Martin’s bet that Georgia was edging away from the old South and toward the new–going the way of Virginia and North Carolina, as opposed to Alabama and Mississippi–proved right. When the economy went south in September, Obama’s numbers went up–nationally and in Georgia–and so did Martin’s. Suddenly, the unwinnable race was within reach. And because of the unusual Georgia law that requires a winning candidate for statewide office to gain more than 50 percent of the vote, “within reach” was good enough. On November 4 Chambliss won 49.8 percent, Martin took 46.8 percent and a Libertarian, the remainder. That result set up a December 2 runoff that is arguably the most high-stakes Senate race the country has seen in years. At issue is not just the possibility that Democrats could secure sixty seats in the chamber–a prospect that requires Minnesota Democrat Al Franken to prevail in a recount fight with Norm Coleman and Martin to beat Chambliss. The Georgia runoff is, as well, the first test of Obama’s mandate–and of his willingness to spend political capital to extend it. Perhaps more significant, the Georgia contest will provide as clear a signal as we’ve yet gotten regarding the extent to which candidates can or will compete as unapologetically “national” Democrats in a region that over the past quarter-century has become the GOP heartland.

This is where the runoff gets complicated for the Democrats. The Peach State may be tipping in the party’s direction, but it hasn’t yet fallen their way, as Virginia and North Carolina did. Georgia Democrats have strongholds in the Atlanta area and in rural counties with large African-American populations. And as retirees and refugees from colder climes have settled around coastal cities like Savannah, Georgia Democrats have begun showing strength in areas where they once had a hard time competing. But will that strength manifest itself December 2?

Schumer’s DSCC is in with advertising and Bill Clinton. And Martin’s populist appeal, which highlights Chambliss’s McCain-like uncertainty about how serious the nation’s economic troubles have become, should have multiracial appeal in a state where Democratic candidates must attract African-American as well as white working-class voters. Still, Chambliss has the advantages of incumbency, a determined push by Senate Republicans and their allies to spend what it takes to prevent Democrats from attaining a filibuster-proof majority–and, potentially, election fatigue: if turnout settles back toward normal patterns, the incumbent wins. Martin’s chances are rooted in the prospect that Obama really has created a national movement capable of maximizing Democratic turnout even when the president-elect’s name isn’t on the ballot. Martin is making the connection, declaring that “America has elected Barack Obama president, and now is the time for us to help him succeed.”

Obama’s team has helped some, keeping campaign offices open, with staffers delivering the “Obama needs Martin” message. But Martin needs Obama. And that’s the challenge. If the president-elect makes a serious campaign swing in Georgia, he could generate the turnout among black and young voters that his party’s Senate nominee requires. But such a move would call into question Obama’s bipartisan positioning during the transition, and it still might not prevent the Chambliss win that Republicans would paint as a rebuke to the new president. In a sense, then, Georgia will be a measure of the extent to which Obama is serious about making all that campaign talk about a fifty-state strategy a reality for his party. Going into Georgia for Martin involves a real risk for Obama. Yet it is in Georgia that Obama could prove that his victory was more than just a personal triumph–that it was, in fact, the beginning of a generational realignment that will extend deeper south than most Democrats–and all Republicans–dared imagine.