Rep. Jim Marshall (D-Ga.) held on to his Macon-based seat by the skin of his teeth in 2006, and he’s positioned to do the same on Election Day.

A new poll conducted exclusively for Roll Call found Marshall clinging to a narrow lead over his Republican challenger, retired Air Force Maj. Gen. Rick Goddard. And the size of the African-American turnout might determine just how close the race ultimately is.

In the poll, taken by the automated firm SurveyUSA on Saturday and Sunday, Marshall had 49 percent and Goddard had 45 percent. The poll of 634 likely voters had a 4-point margin of error.

The perception among many political observers was that Marshall had a more substantial lead over Goddard, a novice candidate despite his impressive military credentials. But the race might be closing fast, which was also the case in 2006, when the Congressman edged ex-Rep. Mac Collins (R) by 1 point, even though it was a strong year for Democrats nationally — and polls had showed Marshall with a slightly bigger lead. The Marshall-Collins race was one of the 10 closest House contests of last cycle.

The 8th district is conservative. President Bush took 61 percent of the vote there in 2004, and even today, when Bush’s poll numbers nationally are abysmal, 40 percent of 8th district voters said they approved of his job performance.

That conservative bent is also reflected in the 2008 presidential matchup in the Roll Call poll. Sen. John McCain (R-Ariz.), whose overall lead in Georgia appears ever more tenuous, had an advantage of 56 percent to 40 percent over Sen. Barack Obama (D-Ill.) in the 8th district, according to SurveyUSA.

When asked which party was better equipped to handle the nation’s economic crisis, 56 percent of the district’s voters said the Republicans, while 39 percent said the Democrats — a number that is at odds with the nationwide trend.

But African-American voters might be the wild card in the 8th district equation. Blacks make up one-third of the district’s population and accounted for 31 percent of the voters queried by SurveyUSA. If the black turnout is higher — and experts are predicting a record turnout of African-American voters in statewide thanks to Obama’s candidacy — then Marshall’s margin over Goddard could improve. Marshall had a 9-1 advantage over Goddard among black voters in the poll; Goddard had a 2-1 lead in the white vote.

Marshall can also take comfort in that he led among poll respondents who had already voted by 8 percent; he and Goddard were tied among those who had not yet gone to the polls.

But Goddard is one of the top Republican recruits of the cycle. He is the former commander of the massive Warner Robins Air Logistics Center at Robins Air Force Base, the biggest employer in the district, and is a well-known and popular figure throughout the area.

Still, in a pro-military district, Marshall has an impeccable military background as well. An Army brat, he dropped out of Princeton University in 1968 to become an Army Ranger and serve in Vietnam. He was wounded in combat twice and was awarded the Purple Heart.

Marshall is one of the most conservative Democrats in Congress, occasionally even racking up a higher score from the American Conservative Union than he does from the liberal Americans for Democratic Action. In the Roll Call poll, 27 percent of self-identified conservatives cast their lot with Marshall instead of Goddard. By contrast, just 14 percent of conservatives expressed a preference for Obama in the presidential trial heat.

Marshall, a former mayor of Macon, first ran for Congress in 2000, losing to then-Rep. Saxby Chambliss (R). He narrowly won an open seat in a redrawn district two years later, at the same time that Chambliss was elected to the Senate.

After Marshall won a surprisingly easy re-election in 2004, Georgia Republicans redrew his district to make it more difficult for him the next time. They succeeded — and the Congressman continues to face political peril as a result.