Virginia state Del. Gwendalyn F. Cody of Annandale fixes a visitor with a quizzical look.

"Don't you know," says she, "that I'm running against the entire Democratic Party?"

Cody may not be too far from the truth.

A two-term delegate and conservative Republican, Cody, 63, is regarded by members of both parties as one of the most vulnerable incumbents in the Northern Virginia delegation in the Nov. 5 elections.

The principal reason: A newspaper poll last winter ranking the effectiveness of state legislators put Cody 100th -- dead last -- among members of the House of Delegates.

Democrats, who at every opportunity trumpet the results of that poll, say they have targeted Cody for defeat and that in Leslie Byrne, a 38-year-old civic activist and businesswoman, they have a tireless campaigner and candidate who can win.

"She [Cody] is not taken that seriously," charged Del. Vivian E. Watts, the Democrat who represents an adjacent Fairfax County district. "She is very flamboyant and has a tendency to speak out on an issue out of emotion." Watts says Cody is known as "Wild Bills Cody" in the legislature for the measures she introduces, and Watts added: "I'm being less harsh than I could be."

Republicans reject those charges as inaccurate and unfair. "I think she does a very good job and is effective," said House Minority Leader Vincent F. Callahan Jr. of McLean. "I think she is liked, not afraid to speak up on the issues. And sometimes it takes guts to do that."

Cody counters that Byrne lacks the experience to serve in the General Assembly. "She's been down there two weeks and becomes an instant expert," she said of Byrne's work as an aide to Watts.

The 38th is regarded by most politicians as a "swing" district with many voters committed to neither party. The district is covers a slice of east-central Fairfax County bordering Arlington County in the east and stretching nearly to Fairfax City in the west. The district, most of which lies inside the Capital Beltway, is heavily developed, packed with apartment buildings, town houses and some affluent neighborhoods of single-family homes.

Cody was first elected in 1981, lost narrowly in the 1982 special elections after redistricting and returned to beat the Democratic incumbent in 1983.

Cody, a public policy resercher, and Byrne have raised about $20,000 each and plan radio advertising in the last week of the race.

The contest, the candidates agree, has not focused on issues other than effectiveness, even though Byrne and Cody are not of the same ideological bent.

Cody's campaign literature cites her support for rights of the disabled, as well as higher state funding for education and road building. In the past, she has billed herself as a "Ronald Reagan conservative" and made her opposition to the Equal Rights Amendment a centerpiece of campaigns with statements such as: "I'm for the 'ER' but I'm not for the 'A'."

While Byrne's position papers are more extensive -- she has issued statements on a range of issues, including a variety of women's and family issues and a call for legislation permitting broader powers for local governments in controlling land use -- she acknowledges that she and Cody have yet to clash on such issues.

Rather, the campaign has turned on the issue of Cody's effectiveness. Specifically, the candidates have clashed repeatedly on the survey taken by the Norfolk Virginian-Pilot and Ledger-Star in which Cody was ranked as the least effective member of the House.

Cody and many other Republicans deride the survey, saying that it was biased in favor of Democrats, who hold a large majority in both chambers of the General Assembly. In fact, eight Northern Virginia Republicans are among the bottom-ranked 25 delegates.

Cody attributes her rating in the survey -- which queries state officials, legislators, lobbyists and reporters -- to her status as a Republican woman and junior member of the House. Calling the poll "a political cutesie," Cody said, "You have a Chinaman's chance when you're a Republican and a new member." She added: "I'm not down there [in Richmond] for a popularity contest."

To Byrne, the survey is potent ammunition. "The poll is a substantiation of what people who are working [in Richmond] already know," she said, "that [Cody]is the least effective member down there."

She says that Cody has lost respect among her legislative colleagues for being on the losing end of lopsided votes on popular bills.

Byrne says she is getting her message out with an aggressive door-to-door campaign. She says she has knocked on 5,600 doors and worn out three pairs of shoes.

Cody, who graduated from the University of Puget Sound and has taken graduate courses at four other colleges, points out that Byrne did not graduate from college. Byrne, who now is a principal in a small firm that recruits workers for high-tech companies, replies that she left college to go to work.

Cody says she is avoiding discussing her opponent's broadsides -- "I haven't mentioned her name and I don't plan to" -- a typically Virginian tactic that may be intended to deprive Byrne of the name recognition she needs.

Cody is also knocking on doors, but she complains that she is hampered by legislative responsibilities. "I'm not a politician," she declared, "I'm a legislator."

Politicians say Cody is counting heavily on the political backing of Fairfax Supervisor Thomas M. Davis III, a Republican whose Mason District includes all but a handful of the precincts comprising the House district.

Davis, who is extremely popular in the area (he captured 76 percent of the vote in his 1983 reelection bid), is honorary chairman of Cody's campaign and has helped raise money for her. The extent to which he campaigns actively for Cody in the final weeks of the race could prove pivotal, some politicians say.

Cody, who will soon become a grandmother, acknowledged she faces a tough race. "You have to take calculated risks," she said, adding: "I want you to know that I win at blackjack."