After Rep. Stan Parris leveled a series of blistering attacks on his Republican opponent for governor, aides to Wyatt B. Durrette decided it was time for Durrette to return fire and approached him with a draft letter.

"Dear Fellow Republicans," the letter began. "I am angry . . . Stan has flooded the mail with highly negative attacks on my record . . . . Stan's distortions are deliberate . . . . Such calculated misrepresentation . . . is intolerable."

Though they knew the letter accurately expressed Durrette's feelings, the aides were worried. Durrette, a 47-year-old Richmond lawyer and former legislator from Fairfax County, was known for being too much of the genteel Virginia politician to reply to opponents' assaults.

This time, however, Durrette put aside any such reservations. To many Republicans, the two-page letter that went out in January was a sign of how Durrette, who last week apparently defeated Parris for the nomination, has changed since narrowly losing two statewide races in the past eight years.

Before him looms an election that supporters say will either vindicate those who stood by him as a warm and electable conservative leader or will vanquish him forever as a candidate. "If I lose, that's it, no question about it," Durrette said.

The November election apparently will pit the balding and athletic favorite of the GOP party regulars against Gerald L. Baliles, a Richmond lawyer who beat Durrette by 2 percentage points for the office of state attorney general four years ago in the landslide that put Gov. Charles S. Robb in office.

In the estimation of a number of Republicans, this latest chapter in Durrette's up-and-down political life finds him at the peak of his political powers.

He speaks forcefully, without notes, shaping the air with his hands to illustrate a point and demonstrating the skills of expression honed in numerous courtroom trials and 13 years of political campaigns. In a crowd of supporters, he comes across as confident and approachable, sprinkling his conversation with words like "super" and "incredible."

He has backing throughout the Republican Party, though he is criticized by a number of GOP moderates who say he abandoned the moderate ground he once occupied as his aspirations for statewide office rose.

"That's the one thing that makes me uncomfortable," said one prominent Northern Virginia Republican. "When you change a lot of views, it's more likely to be on the basis of the political winds than on conviction. I'm not convinced that some of the views he is now embracing weren't adopted to further his political career."

Durrette, who moved from Fairfax County to Richmond two years ago, also professes to have substantial support from Richmond's Main Street crowd -- the loose coalition of wealthy businessmen who will send their checks to a Republican or Democrat, depending on who they think is the best conservative.

The supporters came despite the fact that after his 1981 loss to Baliles, a good segment of his party considered Durrette finished politically. Durrette himself debated for months about whether he had a future as a political candidate after the night he conceded defeat in a Richmond hotel suite, his voice cracking with emotion.

Though political experts attributed Durrette's loss largely to Robb's coattails, it came on the heels of his failure to hang onto the party's nomination for attorney general in 1977.

In what Durrette now considers the biggest error of his political career, he turned his supporters loose to work for other candidates while his rival for the nomination, J. Marshall Coleman, was drumming up votes at the party's convention at the Roanoke Civic Center. In the space of a day, Durrette's lead eroded and Coleman claimed the nomination by a fraction of a vote while Durrette stood shocked and motionless on the convention floor.

Ed DeBolt, Durrette's chief campaign consultant, remembers the reaction when Durrette's name came up as the party's possible candidate for governor after 1981: " 'Oh yeah, sure. He doesn't have a base. He lost before. We'll find somebody else.' But Wyatt has very calmly and systematically gone about building his support."

With moves such as his response to Parris' letter, Durrette appears to have answered a concern that many like DeBolt shared: "He's a nice guy but he's not tough enough."

"Now when Wyatt says to me, 'I will call this person and solve that,' I know he will," said DeBolt. Before it was: "I hope he will, I hope it's okay."

Durrette agreed that he is "more determined this time." He is also, according to some supporters as well as critics, more conservative than he once was.

The son of a foreman at a paper mill, Durrette grew up in southeastern Virginia's poor and rural Southampton County in a family of "Democrats, if they were anything."

He was won over to a conservative philosophy of government while in law school at Washington and Lee University in western Virginia. To promote his views, he founded the Washington and Lee Conservative Society and put out a newsletter, "The Southern Conservative." As a graduate student, he headed a Youth for Goldwater chapter.

His conservative philosophy was not as evident a decade later in the Virginia General Assembly. Between 1972 and 1978, when he represented Fairfax County, he was regarded as a moderate. In the view of a number of his colleagues, Durrette went about altering that image during the latter part of his legislative career to increase his appeal as a statewide candidate.

"He was catering to the conservatives," said Rep. James H. Dillard (R-Fairfax), a Parris supporter. "He changed his positions on a number of items and lost the admiration of the moderates in the party."

Durrette repudiated his support of the Equal Rights Amendment, his cosponsorship of "meet and confer" legislation that would allow localities to discuss salaries and working conditions with union groups, and his support for proposals to allow voters to decide in a referendum whether the state should allow parimutuel gambling or a state lottery.

His views on day care regulation also appear somewhat different. In 1979, he and fellow members of an advisory board asked then-governor John N. Dalton to veto a measure exempting the centers, arguing in part that the centers needed to be regulated. Now Durrette says that if he supports any change, it would be to end all state regulation of day care centers.

On other issues, his stand is the same but his line of argument has shifted subtly. In 1976, for example, he told a reporter he was skeptical of a bill that imposed one-year mandatory sentences for use of a gun in the commission of a felony, despite his vote to pass it, because it "contradicted a basic American value that each individual should be judged individually." Now he says he was skeptical because "it wasn't stiff enough."

He was also arguing in 1975 for "effective consumer advocacy" before the State Corporation Commission, which regulates utility rates. In 1976, he sponsored a measure that would have taken the job of representing the consumers away from the state attorney general's office and given it to a new Department of Consumer Counsel, a move favored by proconsumer legislators. His explanation for the measure now is that the attorney general's office was unfairly favoring consumers and "crusading against the utilities" for political reasons.

Durrette says he altered his positions after he was convinced by more reading or debate that they were wrong, and then "only on a couple of issues. Other than that I don't think my views have changed."

He points to his support for Ronald Reagan over President Ford in 1976 as an example of his staunch conservatism.

Few doubt he would veer from a conservative agenda as governor. He promises, for example, to work actively for a controversial proposal to restrict abortions for minors. Baliles has said he would veto any such measure.

"I don't think he'd rock any boats," said House Minority Leader Vincent F. Callahan (R-Fairfax). "He'd be conservative but a progressive governor at the same time. He'd be a governor very much in Virginia tradition."

Durrette's record as a legislator wins praise from former colleagues, including some critics such as Dillard. He is credited with putting through a complicated revision of the juvenile code and setting up a state office to aid volunteer organizations. "He was really very good," said Del. Dorothy S. McDiarmid (D-Fairfax), who worked with him on the juvenile code legislation.

Children and volunteer efforts are favorite themes for Durrette. As a young lawyer in Fairfax, he and his wife Cheryn, a former beauty queen, offered their home as a temporary shelter when the juvenile detention home grew too crowded. About eight years ago, they adopted a Korean baby. Asked what achievement gives him the most pride, Durrette points immediately to a picture of his family on the wall of his campaign office.

Near the photo is another square frame with telling contents, a saying that struck Durrette so much he had it copied for his campaign staff: "Life's greatest glory lies not in falling again, but in rising every time you fall."