Republican and Democratic party leaders say it would take a miracle for independent Daniel Belsole to defeat Republican Thomas M. Davis III in the Fairfax County Board of Supervisors race in November. But then, Belsole believes in miracles.

An antique car company owner, Belsole is semiretired and spends much of his time praying for hospital patients and anyone else who asks. He hands out cards that read: "Ministering God's Healing Love to Catholics, Protestants and Jews." He has never held elected office.

Davis, who is seeking his third term as the Mason District supervisor, is one of the most popular elected officials in Northern Virginia. In 1983 he won 77 percent of the vote, and many believe that the Democrats did not field a candidate against him this time for fear that Davis would draw Republicans to the polls, helping Republican board Chairman John F. Herrity, considered to be in a close race with Democrat Audrey Moore.

The Mason District is a densely populated area mostly inside the Capital Beltway that runs from Seven Corners in the north to Lincolnia in the south. Columbia Pike cuts an east-west line through its midsection.

So far, there has been little campaigning on either side. "I didn't even know Tom had any opposition, that's how low-key that race is," said Chuck Weir, the Republican Party chairman for the 10th Congressional District.

Davis, a 38-year-old lawyer, said he expects to spend $10,000 to $15,000 on the campaign, compared with some other supervisors who will spend $60,000 or more seeking reelection.

Belsole, 55, has taken the unusual step of announcing that he will refuse all campaign contributions. He said he will finance his bid with $30,000 of his own money. "I haven't taken one penny or dollar from anybody," he explained. "This is strictly my thing." He said that because people are aware of his position, he has not received any money.

Davis chuckled at Belsole's refusal to accept campaign donations: "That's easy. He's not taking any money because nobody is offering it."

The Republican said he is running on his record and does not believe that the voters want a change. Weir agreed. "He still has a long, long honeymoon with the people," he said of Davis.

But Belsole said he has done some door-knocking and has found that Davis "is not so popular. He has been voting with the developers."

However, Davis was a strong supporter of a "downzoning" measure last December that developers fought ardently against. The measure would have drastically reduced the amount of construction permitted on land zoned for industrial use; it was defeated on a 5-to-4 vote.

If elected, Belsole promised to donate his $35,000 supervisor's salary to a Mason District legal defense fund that would be used if the district residents decided to challenge developers who were building unwanted construction, the Federal Aviation Administration because of heavy air traffic, or other groups.

"I'm only talking to civic associations and the NAACP," Belsole said. "I'm refusing invitations from special interest groups. I don't want to be pressured in any way. I don't want any restrictions once I get in office."

An 18-year Fairfax resident, Belsole said he was prompted to run because he finally had the time and was tired of crime, heavy traffic and development. Davis said Belsole has no credentials to run: "Crime is his big issue, and he has not even been active in his Neighborhood Watch program."

Born in Latrobe, Pa., Belsole has been an aficionado of antique cars since he was a child. Recently he built a Ferrari from scratch in his garage.

Davis grew up in Arlington and has been involved in politics since he was a congressional page at age 14.