Virginia Lt. Gov.-elect L. Douglas Wilder, whose victory last month came despite early predictions that his campaign was doomed, formed an "underdog fund" today to help Democrats across the country whose campaigns are given little chance of succeeding.

The fund, organized under Virginia law as a political action committee, will be financed initially with about $50,000 left over from Wilder's uphill campaign.

Paul Goldman, who directed Wilder's campaign, called the PAC "innovative -- there's nothing quite like it anywhere." It will provide technical assistance -- most likely in the form of Goldman's time -- to "experienced and qualified Democrats" whose campaigns "need a little boost," he said.

"Selected underdog candidates will be offered a full range of campaign expertise," including advice on advertising and polling, but the fund will make no monetary awards, according to a statement filed today with the Virginia Board of Elections.

Goldman said the PAC was formed in response to calls Wilder got from around the country following his Nov. 5 upset of Republican state Sen. John H. Chichester of Stafford County. The victory made Wilder, a Richmond lawyer and state senator, the first black to win a major state office in the South since Reconstruction.

Many of the congratulatory calls came from would-be candidates in other states who asked, "How did you do it?" Goldman said.

"We can't do 100 people," said Goldman. But the aide said Wilder "wanted to do something to demonstrate" his appreciation for the encouragement he has gotten around the country.

Goldman said the fund will assist candidates who, like Wilder, are "people with lots of experience, but who can't get started, or are told they can't win." Goldman said the fund will not single out minority candidates.

The fund will not award cash, because Goldman said the money wouldn't go far enough and because it might be against the law in some states. He said the fund will pay for the services of "myself and some others" whose work could help hold down the costs of campaigning.

Although the start-up money will come from the surplus that remains from Wilder's campaign -- the final accounting is due Thursday -- Goldman said officials may seek contributions to the fund if they find enough candidates to support.

He said that although there are no statewide races in Virginia next year, 1986 is a big year for state elections elsewhere. Wilder could not be reached for comment.

After his 1981 election, Gov. Charles S. Robb formed a political action committee called "Virginians for Good Government," which critics dubbed "ChuckPac." Its stated purpose was to help Democratic candidates for the Virginia House of Delegates, but it proved to be controversial and was disbanded a year after its existence was disclosed.

That PAC began with $95,000 left over from Robb's campaign, and was augmented with money raised at three fund-raising events held around the state. Its major beneficiary was the Virginia Democratic Party, which received about $125,000 for legislative candidates.

A $16,000 expenditure, listed as going to the state's general fund, was used to renovate a garage at the governor's mansion for Robb's wife, Lynda, and $20,000 went to the Virginia Women's Cultural History Project, a federal-private program headed by Lynda Robb. The other principal recipient, which got $22,000, was the Democratic Governors Association, of which Robb was chairman-elect at the time.