The sun had already set on a long day of campaigning and the air was getting chilly. Yet Audrey E. Scott could not resist knocking at one last house in the northern Prince George's County neighborhood.

"Hello!" she said brightly as a man answered the door. "I'm running for county executive, and I hope I can count on your support."

The man gave her a wry look. "Well, I'm 85 years old and I've never voted for a Republican, so that's not in your favor," he said.

Scott didn't miss a beat. "This may be the year!" she replied, grinning broadly and handing him a flier. "I'm going to give you my number so you can call me if you have any questions."

The moment was vintage Scott -- a classic display of the mix of charm, substance and grit that the former Bowie mayor and current County Council member has relied on to win repeatedly in her majority Democratic district.

Except that this voter wasn't buying Scott's pitch. "You're a nice lady so I'm trying to be nice," he said with a parting wave. "But I will not be calling you."

Armed with a detailed plan to fix the county's troubled schools, endorsements from such media outlets as The Washington Post, and a wealth of experience as a local legislator and former senior federal housing official and teacher, Scott, 66, is mounting a spirited campaign to become the first Republican elected Prince George's county executive since 1978.

If she wins, it would be only the latest improbable triumph for the daughter of a crane operator who began life in poverty and went on to become the first woman elected mayor of Bowie and the first Republican elected to the council in 24 years.

But Scott may finally be pushing the limits of her crossover appeal.

Until now, her victories have been in races where Democrats have outnumbered Republicans by less than 3 to 1. This time she's running countywide, where Democrats rule 5 to 1.

Scott also faces an opponent, State's Attorney Jack B. Johnson, who has already won election to his countywide office twice and who sailed to victory in the Democratic Party's five-way primary with 37 percent of the vote.

Finally, she is a white person running against a black man in a majority black county that took great pride in electing its first black county executive, Wayne K. Curry, just eight years ago.

These factors all point to a simple conclusion, said Maryland pollster Keith Haller: "It would be a political miracle for Scott to win."

Scott, however, dismisses such talk. "I don't believe my opponent is competent or experienced enough to run this county, whereas I have the breadth and depth of experience that's needed," she said. "So I absolutely believe this [election] is winnable."

It is a can-do attitude that has served Scott well since her earliest days growing up in the rural outskirts of Woburn, Mass.

Her father and her mother, who was a homemaker, never earned enough to buy the family a car, let alone a house.

Scott said she first realized how poor they were on a Christmas morning when she was about 10. For as long as she could remember, Scott had been making do with her older brothers' hand-me-down, black boys' ice skates. All she wanted for Christmas was her own pair of new white girls' skates.

But when the fateful morning arrived, Scott opened her presents to find a homemade dress and bathrobe that her mother had sown out of a flowered chicken feed bag.

The memory remains traumatic, Scott said, "because I now know how much I hurt my parents' feelings by being so upset."

Yet more often than not Scott's family was able to avoid deprivation through resourcefulness and hard work. Her parents kept a large vegetable garden and a chicken coop, so they were never short of food.

Scott herself began picking blueberries and selling them door-to-door at age 5. By the time she was 9, she had saved enough pennies to buy a brand-new bike. Through such experiences, Scott said, her parents taught her the core value at the heart of her identification with the Republican Party: self-reliance.

"I believe in individual responsibility," she said. "I believe that you have to challenge the individual to develop to his full potential and without that challenge you shortchange him."

The strength of that conviction is the reason Scott has never agreed to change parties despite entreaties from Democratic leaders, she said.

"[This belief] has been the key to my success. It underlies everything I do and think; it's just who I am," she said. "So for me to register as a Democrat would be contradicting my principles."

Outgoing and energetic, Scott excelled in school. She won a full scholarship to Tufts University, where she majored in English, and she went on to receive a master's in legislative affairs from George Washington University.

After graduating from Tufts in 1957, Scott became an elementary school teacher, working in France and Japan to teach the children of American officials overseas.

It was in Japan that she met her husband, John Scott, a quiet electrical engineer who worked for the National Security Agency. In 1966, John took an assignment at NSA headquarters and the young couple moved into a ranch house in Bowie, where they continue to live today.

Scott's plan was to stay at home and raise her four young boys. But by the late 1960s, she was drawn into a protracted community battle to persuade local officials to build the Bowie Health Center.

Her experience in that successful campaign prompted Scott to run for a seat in Maryland's House of Delegates that year. She lost, but made a strong showing. The following year she won a seat on the Bowie City Council and then, in 1976, became the city's first female mayor.

Twice during her three terms as mayor, Scott made attempts to win higher office -- first in the State House and then in Congress. Twice she failed, the second time losing to Steny H. Hoyer, who had been a state senator for 12 years, in a race that attracted national attention.

The day after the election, officials in the Reagan administration called up to offer her a job in the Department of Housing and Urban and Development. By the time she left HUD in 1991, Scott was a deputy assistant secretary.

Three years later Scott won another groundbreaking victory, to the County Council seat representing the 4th District, which includes Bowie and Greenbelt.

Once on the council, she quickly won over Democratic colleagues. "I was surprised at how much I enjoyed working with Audrey," said Vice Chairman Dorothy F. Bailey (D-Temple Hills). "She's very forthright and sharp as a whip. She's also funny and caring."

And Scott is able to move easily among African Americans, said Bailey. "We've been in places where she's the only white person and she's just as comfortable as I am."

Scott also quickly cemented her popularity with constituents, proving an attentive legislator and winning her second term without opposition.

However Scott has also often taken controversial positions that reflect her Republican outlook. She has vigorously opposed efforts to repeal the county's voter-imposed property tax cap, known as TRIM, and favored a measure allowing developers to build in areas of the county where schools are crowded if they pay a fee -- although Scott stressed the law needs fine-tuning.

Some of those stands have led to clashes with Bowie Mayor G. Frederick Robinson, who also has said Bowie has not gotten its fair share of resources from the council. "Different people will have different explanations for that," he said.

Despite her energy, Scott has been hampered by her inability to win endorsements from prominent Democrats. Even Bailey demurred.

But though the odds are against her, Scott also has little to lose.

Term limits bar her from seeking a third term on the council. Her plan to run for Maryland governor was sidelined by Republican Rep. Robert L. Ehrlich Jr.'s decision to enter the race. And her hopes of becoming his lieutenant governor were dashed when he chose another Prince George's Republican, Michael S. Steele.

And even if she loses, Scott may still benefit Ehrlich by turning out the Republican vote in the county -- a service for which political insiders speculate she might be rewarded with a plum position in the state or federal government.

Scott, though, is not acting like someone merely going through the motions. Instead, she is out shaking hands with commuters at Metro stations just after dawn, waving signs at busy intersections for long stretches and knocking on doors well into the dinner hour.

Then she is off to speak at any radio show or citizens' forum that will have her -- even though several such events have been canceled when Johnson declined to appear.

Scott, who said she has raised about $301,000 for her campaign, also recently launched a series of radio and television advertisements attacking Johnson's record as state's attorney.

Johnson has responded that her attacks are unfair and even mean-spirited, and that Scott is taking cases out of context.

Scott said she is merely doing what Johnson invited voters to do: looking at his record. "It's not mean-spirited if it's based on fact."

Her hope is that voters will be disappointed enough to look for an alternative. But can she persuade those voters to choose her instead?

"I'm doing the absolute best I can," she said.

Audrey E. Scott, who has helped raise funds for improvements at Longfields Elementary, visits Vice Principal Jeffrey Holmes and nurse Nancy Lytle. Audrey E. Scott, who has twice been elected to the Prince George's County Council as a Republican, greets Michael Lindsey of Riverdale as she campaigns for county executive.