A federal judge yesterday temporarily blocked an Alexandria computer company from providing Virginia Democrats with sophisticated voter lists that the Republicans contend they have developed during a decade of election victories in the state.

The state Republican Party and Virginia Computer Services Inc. of Haymarket contend that the VSE Corp. of Alexandria is selling the Democrats lists produced through unique computer programs that the Haymarket firm developed for the GOP.

District Judge Oren R. Lewis yesterday issued a temporary restraining order in the case, believed to be one of the first computer suits in the nation involving political parties. Lewis will hear additional arguments in the case this morning in Alexandria.

The judge's order cited a sworn statement by Karen Blocher, president of Virginia Computer Services, alleging that the use of the computer programs by the Democrats "would eliminate a substantial competitive advantage enjoyed by the Republican Party of Virginia."

Blocher said the programs had been turned over to VSE Corp. to use in developing voter registration lists for the Republicans on the condition" that the programs were private and confidential and to be used only for the Republican party . . .

VSE Corp. lawyer Rodney F. Page said the company has long held contracts with both political parties to develop voter lists and that the firm denies any wrongdoing.

"I whink my clients are caught in the middle of something going on between Democrats and Republicans," said Page. "Our people haven't given anything to one that should go to another."

But while Republican Party executive director Jeff Gregson in Richmond refused comment, a party source claimed that the suit is not a political move.

"What you have here is a breach of trust by the company," the source said. "If it wasn't two political parties involved, you'd call it industrial espionage."

According to Republican party attorney Wyatt B. Durrette Jr., a former state delegate from Fairfax County, the programs were designed to help computers digest raw lists of names and addressed from the state's registered voter rolls, which are public records that both parties purchase.

The programs help computers sort out misspelled names, wrong addresses and street numbers and other kinds of mistakes that campaign workers say are commonly found on the voter lists.

The computer-improved lists are then used for mailings, phone campaigns and other efforts to reach voters.

A Republican source said the programs were first designed by Virginia Computer Services for the successful 1973 GOP gubernatorial campaign of Mills E. Godwin. The source said the programs, which cost between $50,000 and $100,000 to develop, were a crucial factor in Godwin's narrow victory over then-Lt. Gov. Henry Howell and have been used, with revisions, ever since.

"The Republican Party is generally credited with being about three years ahead of the Democrats in this state and this has been the competitive edge," said the source.

The source said Blocher, who could not be reached for comment, recently spotted similarities in the lists VSE Corp. was selling to the Democrats.

"Any good programmer salts their programs with gremlins, little mistakes that indicate where a list came from," said the source. "She [Blocher] noticed some extreme similarities."

The Democratic Party was not named as a defendant in the suit and Durrette said he has no reason to believe the Democrats did anything improper.

But a Democratic spokesman in Richmond said the party will join VSE Corp. in attempting to have the temporary order dissolved today. Democratic officials refused further comment on the suit.