Arlington's political campaign season got off to a bitter start last night as the challenger for sheriff accused incumbent James A. Gondles Jr. of an unethical relationship with a partner in a firm that Gondles recommended for a county contract.

The allegation, which Gondles denied, was made at a candidate forum sponsored by the Arlington County Civic Federation, an umbrella organization for about 50 neighborhood groups. The event, attended by about 175 people, is considered the traditional kickoff for the county's political contests.

Fourteen candidates for offices ranging from state Senate to county board spoke briefly and then answered questions from the audience. But the sharpest exchanges came in the sheriff's race, an increasingly acrimonious contest between two former friends and colleagues.

Ronald B. Hager, the Republican-backed candidate for sheriff, alleged that sheriff Gondles, a Democrat, has violated the county board's code of ethics through a relationship that went "beyond casual professional conduct" with a female partner in a Los Angeles consulting firm.

Hager said Gondles suggested in 1986 that the firm be awarded a contract to assess the county jail's medical facilities. Hager argued that other agencies would have provided such services for free. Hager asked, "Why then, would Jim Gondles ask Arlington taxpayers to spend their tax dollars unnecessarily?"

Hager, Gondles' former chief deputy, provided no details of the alleged relationship except to say that the sheriff "has detailed this relationship to me and others on many occasions."

Outside the public forum, Gondles firmly denied any impropriety in the proposed contract, which was approved by the county board but never awarded. He said he recommended the Los Angeles firm because its people are "experts in jail medical health care." Gondles added that Hager recommended that the firm be given the contract -- an assertion that Hager denied.

Gondles, who is married, said that "as far as my personal life is concerned, I have no comment. It's my personal life. I will campaign on the issues. I think Ron Hager has struck a low blow in Arlington County politics here this evening."

Hager previously has accused his former boss of mismanagement and spending too much time out of town.

Gondles has generally avoided direct attacks on his opponent, but prominent supporters of the sheriff have accused Hager of improperly using a middleman to buy a truck at a sheriff's auction. Hager has denied wrongdoing in that incident.

In the county board race, the four candidates for two seats struck a common theme in promising to keep booming commercial development from damaging the quality of life in the neighborhoods.

Democratic incumbent Albert C. Eisenberg said he had "fought to confine development tightly to the areas planned." Democrat William T. Newman, a lawyer and challenger for one of the seats, said developers must be required to plan projects "with our way of life in mind so that we can preserve our green space."

The two Republican-backed challengers made similar pledges. Dorothy T. Grotos, who served on the county board from 1976 to 1983, read a passage from a book criticizing Rosslyn's high-rises as cold and unappealing. "Rosslyn took place under the reign of my {Democratic} opponents," she said.

The other Republican challenger, Jane Bartlett, a former president of the Arlington League of Women Voters, said that the county must ensure "that the traffic coming in and out of new projects can be handled on the surrounding streets" and that new developments have quality landscaping and sufficient parking.