CINCINNATI, July 22 - In the Second Congressional District of Ohio, which Republicans have controlled for the last two decades, the quickest route to political oblivion could be the one chosen by Paul L. Hackett: calling President Bush a "chicken hawk" for not serving in Vietnam and harshly criticizing the decision to invade Iraq.
But Mr. Hackett, the Democratic candidate in the Aug. 2 special Congressional election, is not an ordinary politician. Until four months ago, he was serving in the Marines, commanding a civil affairs unit in Iraq.
If Mr. Hackett is elected, he will become the first member of Congress to have served in the Iraq war. That alone has helped Mr. Hackett, a 43-year-old lawyer, unexpectedly turn this potential walkover into a sharply contested race.
"When you tell people he just got back from Iraq, they stop and listen," said Timothy Burke, the chairman of the Democratic Party in Hamilton County, one of seven southern Ohio counties in the district. "He'd not have nearly as many people paying attention to him if it weren't for that initial grabber."
Mr. Hackett's Republican opponent, Jean Schmidt, has poured more than $200,000 of her own money into her campaign and traveled tirelessly across the district. Her campaign has received tens of thousands of dollars from national Republican committees, and Mr. Bush has agreed to record a telephone message that will be delivered the weekend before the special election.
"I'm a runner, and when you are overconfident, that's when you see your competition's shadow," said Ms. Schmidt, 53, who has completed 54 marathons. "And I won't see his."
The candidates are competing to fill the seat held for 12 years by Rob Portman, who resigned to become Mr. Bush's trade representative. Mr. Portman routinely won the district, which stretches from poverty-stricken communities along the Ohio River to affluent Cincinnati suburbs, with more than 70 percent of the vote.
The national Democratic Party initially ignored the race. But Mr. Hackett has changed some minds, and the party has begun dispatching young staff members to the field, hoping to send a message that Mr. Bush is weak in one of his most loyal districts.
In addition, the Democratic strategist James Carville was the headliner of an event in Cincinnati on July 19 that raised nearly $100,000 for Mr. Hackett, who trails Ms. Schmidt in fund-raising three to one. On Thursday, Max Cleland, a former Democratic senator from Georgia and a Vietnam veteran, campaigned with Mr. Hackett, calling his decision to volunteer for Iraq "an act of conscience."
"Someone who has led on the battlefield, that's the kind of person you want to see in the United States Congress," Mr. Cleland said at a rally in Blue Ash.
Mr. Hackett, the son of a traveling salesman, joined the Marine Corps in college and was honorably discharged in 1999. He joined again in 2004, commanding a civil affairs unit in Ramadi and Falluja. A lean 6-foot-4, he is garrulous, profane and quick with a barbed retort or a mischievous joke. He and his wife, Suzi, have three children, ages 8, 4 and 1.
If he loses the race, he says, he will probably return to Iraq next year.
Ms. Schmidt is the daughter of a well-known local banker who owned Indianapolis race car teams on the side. Small, wiry and intense, she exudes seriousness and is given to long pauses before answering questions. She is married to an investment counselor, Peter, and they have a 27-year-old daughter.
Mr. Hackett, who said he had never had political ambitions before, jumped into the race the day he returned from Iraq in March when a friend told him about Mr. Portman's nomination.
Ms. Schmidt, a former state representative, said she formed an exploratory committee, studied a straw poll and contemplated the race for a week before joining the crowded Republican primary.
The candidates are even more different on most issues. Ms. Schmidt supports making Mr. Bush's tax cuts permanent, but offers no plans for closing the federal deficit other than trimming "unnecessary pork" and bureaucratic inefficiency.
Mr. Hackett opposes making those cuts permanent, asserting that troops in Iraq are not receiving adequate supplies or benefits.
Ms. Schmidt, a leader of Right to Life of Greater Cincinnati, wants abortion outlawed. Mr. Hackett says he opposes abortion but believes government should not dictate a woman's health care decisions.
The two, however, support broad gun rights. His opposition to banning assault weapons has gotten Mr. Hackett, who says he owns military-style rifles and has a permit to carry concealed weapons, into arguments with many Democrats.
"The Democratic Party is wrong on this," he said. "We don't want government dictating a woman's right to choose. How do I tell people it's O.K. to dictate their gun ownership?"
Mr. Bush has also emerged as an issue. Ms. Schmidt contends people in the district, which voted 64 percent for Mr. Bush last year, adore the president. Her only difference with the administration, she said, is on Mr. Bush's proposal to create private accounts in Social Security, which she says could be risky.
Mr. Hackett has been bluntly dismissive of Mr. Bush, saying the United States should have focused on capturing Osama bin Laden instead of invading Iraq so quickly. In a public forum, he called Mr. Bush the biggest threat facing the United States, a remark that has infuriated voters, Republicans say.
Yet Mr. Hackett has also tried to exploit Mr. Bush's popularity here, opening his lone television commercial with Mr. Bush saying, "There is no higher calling than service in our armed forces."
Republicans have derided the spot as hypocritical. "I want to win," Mr. Hackett replied.
Democrats are also hoping that disgust with a scandal involving the administration of the Republican governor, Bob Taft, and a Republican coin dealer who is accused of misappropriating $13 million from a state workers compensation fund will hold down Republican turnout.
Mr. Hackett has tried to tarnish Ms. Schmidt's integrity as well, criticizing her for not disclosing free tickets to a Cincinnati Bengals football game she received from a lobbyist last year. Ms. Schmidt blamed the lobbyist for the oversight, and has repaid him $644.
But Ms. Schmidt is a proven battler, having bested several better-known candidates, including Pat DeWine, the son of Senator Mike DeWine, in the primary. She contends that although voters respect Mr. Hackett's military service, it will not be the deciding factor.
At the Warren County fair, where Ms. Schmidt bought a 230-pound pig from a 9-year-old girl and watched a demolition derby, Charles Hartman, a Democrat turned Republican, agreed.
"It's a positive thing for him," Mr. Hartman, a substance-abuse specialist with a nonprofit group, said after meeting Ms. Schmidt. "But we're not at war here."
But Todd Schulte, a Republican, said Mr. Hackett's service had caused him to consider voting Democratic on Aug. 2.
Mr. Schulte, a 40-year-old business owner, happened on Mr. Hackett's event in Blue Ash and was impressed with the candidate's decision to volunteer for Iraq.
"He's got a wife, kids and a good job but he's not sitting in the back row," Mr. Schulte said. "That gives me something to think about."