The contrast is striking.

Democratic state Del. Vivian E. Watts of Annandale is low key and relaxed as she recites a list of her accomplishments as a relatively new junior member of the Virginia House of Delegates.

Her opponent, Republican Robert E. Lee Murphy of Springfield, is animated and intense as he discusses his challenge to Watts -- a race he was not supposed to be involved in at all.

Many Northern Virginia politicians -- Democrats and Republicans -- give Murphy an "A" for aggressiveness but say he faces an uphill fight in his effort to defeat Watts in the Nov. 5 election. He became the GOP candidate by default after Richard N. Vannoy, who narrowly defeated Murphy in the June Republican primary, said he was not up to the demands of a general election and dropped out of the race.

The rhetoric has grown nastier as Watts and Murphy enter the final days of the race for the seat from Virginia's 39th House district, an office that Watts has held for four years after extensive involvement in civic groups as diverse as the League of Women Voters and the Fairfax County Chamber of Commerce.

Watts, who represents what is generally considered a Republican area, had reason to believe that this, her fourth campaign for the legislature, would be the least troublesome. She won high praise from colleagues on both sides of the aisle last year after helping to reshape the state's highway funding formula in a way that will provide much-needed funds for improvements to Northern Virginia's clogged road network.

"Baloney," Murphy declared when asked about Watts' work on the roads issue. "Vivian Watts did no more or no less than any other Northern Virginia legislator."

To underscore his point, Murphy has flooded the district with 500 handmade signs that proclaim: "Traffic Stinks. Get Angry and Vote for Murphy."

That Murphy, a 53-year-old merchant, is attacking her on the traffic question has surprised and angered Watts. "That's been my number one priority," she said in an interview last week. "To use that as his issue, when I have been singled out as the one who has done the most for Northern Virginia to get the funding formula changed, is just incredible to me."

The roads issue only skims the surface of the angry debate in the district, which includes the section of Annandale south of Little River Turnpike (Rte. 236), North Springfield, Lincolnia and Kings Park.

Murphy charges that Watts has voted for bills favorable to her campaign donors, and he characterizes her as a "Jesse Jackson liberal."

He asserts that she relies on personality rather than substance in appealing to voters. "One of the things she tries to do is charm you to death," he said.

Murphy has raised only about $3,000, compared with the estimated $25,000 that Watts said she has raised. Watts acknowledged Murphy's assertion that her largest contributors are groups representing bankers, teachers and real estate brokers, but she said their support is "a measure of my effectiveness. They like a winner."

Watts said that Murphy's attacks are replete with "distortions" and are no more than a "smoke screen" for his political inexperience and relative absence from civic activities. "He just has not paid his dues in Fairfax County," she said.

Watts, 45, is a research consultant at the accounting firm of Arthur Young & Co. in Washington.

In Richmond, she has been credited by Democrats and Republicans with paying attention to details and mastering the art of compromise in a 100-member chamber often sharply divided into camps that represent the state's regions.

"Vivian is a highly respected member of the General Assembly," said state Sen. Wiley L. Mitchell Jr. (R-Alexandria). "She did a superb job of putting together the data and orchestrating the arguments in favor of revising the highway funding formula."

Many Republicans do not give Murphy much of a chance against Watts, who garnered about 70 percent of the vote in her 1983 race. "Most people who are familiar with that district would consider it an upset of major proportions if Watts were to lose," Mitchell said.

Acknowledged as a tireless campaigner, Watts said she has gone door to door in her district to counter Murphy's claims. She described her meetings with residents as "a real learning experience" that has increased her understanding of problems faced by handicapped and elderly persons.

Watts said she would pay closer attention to those problems during the 1986 session. As other priorities, she listed toughening drunk-driving laws and devising a more equitable formula for real estate assessments. She said that her most important task would be to make certain that Northern Virginia holds on to its $21 million Metro transit appropriation from the state.

In his only previous bid for public office, Murphy finished third in a three-man field for a GOP nomination for a state Senate seat in 1983. He was appointed last year as a member of the Fairfax County Industrial Development Authority.