Marshall's GOP opponent, former state Rep. Austin Scott, and national Republicans have been hitting Marshall with ads that paint him as a supporter of runaway spending and a crony of President Obama and House Speaker Nancy Pelosi, who are about as popular as the boll weevil in some parts of this largely rural district.
Marshall, 62, a lawyer and a Purple Heart-decorated Vietnam veteran, has distanced himself from Pelosi and accused Austin of being soft on illegal immigrants. In past races, he has proved himself a tenacious campaigner capable of drawing swing voters and even some crossover Republican support.
Republicans say voters' sour mood toward incumbent Democrats nationally favors Scott, an energetic 40-year-old insurance broker from Ashburn who won his first election at age 26 and touts his walking tours of the state. But few are calling Scott's election a sure thing.
"If he does beat Jim Marshall, it's going to be very close," said Ken DeLoach, a Warner Robins minister whom Scott defeated in the Republican primary in July. "I know several people who vote Republican who are still going to be voting for Marshall. He's got a strong base."
Marshall, a former Macon mayor first elected to Congress in 2002, has built that base by frequently voting against House Democrats when he suspects their agenda conflicts with the mores of his district, which stretches from south Georgia's farm belt to near the Atlanta suburbs.
In the current term of Congress, Marshall voted against Obama's health-care overhaul as well as the cap-and-trade energy bill, and again broke ranks with his party by opposing an end to the military's ban on gays serving openly.
He has joined Republicans and other conservative Democrats opposed to allowing the expiration of tax cuts for the wealthiest Americans passed under President George W. Bush.
"People realize I pay attention to the issues and not the party," Marshall said in a phone interview between floor votes on Capitol Hill. "I recognize both sides swing to the extreme up here, and it's really bad for the country."
In 2008, Marshall captured 57 percent of the vote in defeating Republican Rick Goddard even as GOP presidential candidate John McCain won nearly the same share of the vote from district voters.
Still, Scott sees 2010 as the perfect year to blunt Marshall's support among independents and Republican crossover voters.
He's pressing a case that Marshall, despite any maverick tendencies, has been ineffective at stopping Democrats from running up record budget deficits and expanding the reach of government.
"A vote for Jim Marshall is a vote for Nancy Pelosi," Scott said in an interview before greeting 150 supporters at a fried-fish dinner Thursday in Dublin. "He can't stop her from taking anybody's firearms any more than he could stop her from passing Obamacare."
Asked if he'd support Pelosi for another term as speaker should Democrats keep control of the House, Marshall said he isn't committed to any specific candidate.
"I prefer a moderate, a centrist," Marshall said.
Between bites of catfish and hushpuppies at Scott's Dublin event, retired bank teller Gerrie Anderson says she's fed up with Democrats' runaway spending and wary of their health care overall "that nobody understands."
Anderson says she's voted for Marshall in past elections, but that concerns about Democratic policies have compelled her to support Scott.
"Jim Marshall's a good man and he's done a good job, but it's time to let somebody else do it," Anderson said. "I just don't like the way things are going right now. There's too much government control."
According to federal campaign finance reports, Marshall had $985,400 in his campaign fund as of June 30 compared to $213,415 for Scott, though the deadline was before he won the Republican primary.
Marshall has been attacking Scott with TV ads focused on illegal immigration - namely Scott's 2006 vote against a Georgia House proposal to levy a 5-percent tax on illegal workers wiring money back to their home countries.
The ad quotes a snippet of Scott's floor speech in which he says: "I've got a moral problem with that."
In the same speech, though, Scott said he opposes automatic citizenship for children of illegal immigrants born in the U.S. and supports tough immigration enforcement, though he thinks the burden should fall on Congress. In an interview, Scott said he opposed the wire tax because immigration reform "should be about protecting America and not about punishing individuals."
Charles Sneed, a retired electrician from Byron who tends to vote Democratic, says Marshall's positions are sometimes too conservative for him. But he says the congressman's views fit the district well.
"You know what you've got with Jim Marshall," Sneed said. "He votes pretty well with Republicans and Democrats."
Scott has gone after Marshall for his 2009 votes to pass Obama's $787 billion economic stimulus package and to increase the federal government's debt limit by $290 billion.
The Republican says both votes undermine Marshall's claim to being a budget hawk - though the Democrat has voted against every federal budget since 2003 and co-chairs a House caucus pushing a constitutional amendment to require balanced budgets.
Marshall points to economic studies that show that the economic stimulus helped keep the country from plunging into a deeper recession. Increasing the debt limit, he says, was necessary to prevent the government from defaulting on its debt.
Macon coffee shop owner Greg Smith, an independent who typically votes Republican, says he hasn't seen any benefit from stimulus spending. While he's voted for Marshall in past elections, he's unsure about this November.
"The way I see the stimulus is it was bailing out a bunch of rich buddies of theirs who drove the economy into the ground," Smith said. "And I'm sitting here in an empty coffee shop."