If city Democrats turn out tomorrow in the high numbers and with the enthusiasm party leaders are hoping for, the biggest beneficiary could be in a district that covers Staten Island and southern Brooklyn, where Stephen Harrison has mounted a feisty challenge to Rep. Vito Fossella, a Republican.

Severely under-funded, Mr. Harrison has run under the radar for months, but perhaps sensing momentum, leading Democrats have offered help in the final stretch of the race for the 13th district seat. Senator Schumer and Rep. Anthony Weiner appeared with Mr. Harrison last week, and President Clinton and Senator Clinton have recorded telephone messages for him as he looks to carry off an upset win.

With advantages in fund-raising and name recognition, Mr. Fossella, first elected in 1997, has fought an equally aggressive race, spending more than $1.1 million to his opponent’s $90,000 and repeatedly attacking Mr. Harrison as soft on terrorism. While Democrats outnumber Republicans in the district, Staten Island is known for its conservative leanings.

Political analysts say Mr. Harrison, an attorney and longtime community activist, has fought admirably to make Mr. Fossella sweat it out, but they expect him to fall short in a race Democrats never thought would be tight.

“It’s a closer race than it was going to be six months ago,” a Brooklyn political consultant, Gerry O’Brien, said. He predicted Mr. Fossella would win with between 53% and 57% of the vote. In 2004, the congressman defeated Democrat Frank Barbaro, 59% to 41%.

“It would take a Democratic landslide of staggering proportions to really endanger Fossella in that district,” Mr. O’Brien said.

He also dismissed the appearances of Messrs. Schumer and Weiner in recent days, as well as the help gained from the Clintons leaving “robocall” phone messages for voters. “That’s cheap and easy for them to do,” he said, adding that a more important boost would have been large-money donations.

Another political consultant, Hank Sheinkopf, said that even if Mr. Harrison loses, Democrats would have little regret about the district, given expected gains nationally. “They will have won so many seats across the country that it doesn’t matter,” he said.

The candidates have debated five times, the last coming on October 30 in Bay Ridge, where a couple hundred residents packed into a meeting room at the Shore Hill Senior Center. Lasting less than half an hour, the exchange was contentious amid a raucous audience. Several residents used a question-and-answer period to attack Mr. Fossella for his votes in the House, and a few grew visibly angry with his answers.”Why aren’t you representing your constituents?” one woman screamed.

Mr. Fossella maintained his composure throughout the debate, which occurred on Mr. Harrison’s home turf. He cited local accomplishments, such as helping to keep open the Fort Hamilton military base, and he criticized Mr. Harrison for his opposition to legislation authorizing the National Security Agency’s terrorist wiretapping program.

While the Republican has cast himself as an “independent fighter,” he has made his support for the war on terror a centerpiece of his re-election bid, relentlessly denouncing Mr. Harrison’s calls to bring the troops home from Iraq and his position on the wiretapping program. He has even sent out campaign literature juxtaposing Mr. Harrison with pictures of Osama bin Laden, which Mr. Harrison has called “despicable.”

Mr. Fossella expressed confidence after the debate, saying he would “take the fight to the enemy and not let us be attacked again.” He has also criticized Mr. Harrison’s suggestion that the two-way toll over the Verrazano-Narrows Bridge be reinstated, a position considered unpopular on Staten Island, which accounts for twothirds of the 13th district.

Mr. Harrison, he said, is wrong on the “four T’s: terrorism, taxes, tolls, and traffic.”

The Democrat was also optimistic, saying last week: “If you ask me, the race is a toss-up.”

True to his goal, Mr. Harrison ran the ING New York City Marathon yesterday, finishing with a time of 4:47:38, more than two-and-a-half hours behind the winner. He aims to fare better tomorrow.