In his third bid for state office, Robert E. Lee Murphy minces no words when he talks about his Republican challenge to first-term Democratic state Del. Alan E. Mayer in Virginia's 39th House District.

"I'm the winner," Murphy, a 54-year-old Springfield merchant, said last week. "I'm the person who's going to Richmond."

Political observers from both parties are not convinced. They say the bottom line on Murphy's most recent financial disclosure form, $502 in campaign contributions against incumbent Mayer's $21,552.70, tells the story.

House District 39 is a compact, thickly developed area of southeastern Fairfax County, mostly inside the Capital Beltway, that encompasses the Annandale area. The district is made up of a number of long-established neighborhoods, and has a heavy percentage of retirees, as well as military and government workers.

In an election year when transportation and development are high on the agenda of anyone running for office in Northern Virginia, Murphy is working hard to turn his opponent's performance into a key issue. The self-described conservative accuses the incumbent of being a "yes man" and a "rubber stamp."

Mayer, a retired Central Intelligence Agency official who won a special election to the House of Delegates last year, also thinks effective leadership is a key issue.

"I think anybody who takes a look at my background, record and qualifications will certainly support me," Mayer said. "The way he {Murphy} has phrased the issues is irresponsible and doesn't get to the heart of what the real questions are. He doesn't talk about transportation and growth."

Mayer said he wants a state policy that would protect quiet neighborhood streets from "cut-through traffic" that turns them into major commuter thoroughfares.

His opponent said land development should be slowed, and has a campaign bumper sticker that declares, "Land Developers -- Welcome To Fairfax County, Now Go Home!" Murphy said rules should be stiffened so roads and other public services are in place before developments go up.

But Murphy's nastiest salvos are reserved for the incumbent's voting record.

Among other things, Murphy points to Mayer's vote in favor of a bill later signed into law that requires medical referral agencies engaging in for-profit business to tell clients what criteria they use in recommending a doctor.

Murphy said the bill would allow doctors to receive kickbacks and referral fees for passing patients on to other medical practitioners. Mayer denies the charge, saying his challenger has misconstrued the bill.

Mayer, 62, was a Fairfax County community activist before his move into elective politics. The Lincolnia resident succeeded Democratic Del. Vivian E. Watts, who resigned her House seat in late 1985 to become secretary of transportation and public safety in Gov. Gerald L. Baliles' cabinet.

Mayer, a former Fairfax County Park Authority member, easily defeated Republican Robert E. Dively Jr. in the special election.

Murphy, who distributes Irish and Scottish goods to gift shops, is chairman of the Fairfax County Industrial Development Authority, a bond-issuing agency for the Fairfax Hospital Association.

In 1985, Murphy challenged incumbent Watts in the same House district. She beat him by a nearly 2-to-1 margin. Murphy also lost a race for the GOP nomination for state Senate in 1983.

Though his campaign contributions are paltry compared with Mayer's, Murphy remains upbeat about his chances. But political observers say what Murphy lacks in contributions, he also lacks in political finesse.

"It's really a very unserious campaign," said Harris Miller, Fairfax County Democratic Party Chairman.

Miller said the Republican candidate does not take voters seriously. He cited one of Murphy's campaign posters, one with a huge cartoon of Sylvester the Cat.

Even voters within Murphy's own party have reservations. Louis Wagner, a retiree who lives in Springfield, said he observed Murphy during one of his past campaigns.

"I wasn't too impressed with the guy," said 68-year-old Wagner. "He didn't seem to be sincere about what his beliefs were. He just didn't come across as the kind of candidate I'd want in there."