The night before he withdrew his candidacy for governor of Maryland, State Attorney General Francis (Bill) Burch called 125 friends, financial backers and volunteers to give them advance warning. They could turn off their supporting now that he was gettingout of the race.

Burch's withdrawal dashed more than the hopes of his loyalists - it also put an end to one of the favorite parlor games in Maryland's political circles - comparing this year's Democratic primary fracas with the party scrap of 12 years ago.

The year was 1966 and when Maryland Democrats gathered this summer before the Burch withdrawal, they spoke of the uncanny similarities between this season's gubernatorial primary and the race of 12 years ago that ultimately put Spiro T. Agnew into the governor's mansion, and moved him toward the vice presidency of the United States.

They compared acting Gov. Blair Lee III to candidate Thomas B. Finan, the state attorney general at the time, who like Lee, had the support of everybody in Maryland's political organizations from the outgoing governor to the old-line political clubs in Baltimore.

They compared Baltimore County Executive Theodore G. Venetoulis to the 1966 candidate, then Rep. Cartlon R. Sickles, who like Venetoulis was the darling of the liberals and most of the labor movement.

They compared Harry R. Hughes to 1966 candidate Clarance W. Miles who like Hughes, hailed from the Eastern Shore, practiced law in a silk stocking Baltimore firm the same firm and appealed to Maryland blue bloods. And they compared Burch, the erstwhile conservative of the current campaign, with George P. Mahoney, the far more conservative maverick of 1966 who appealed to Maryland's large working class with his populist campaign rhetoric.

Mahoney won. It was a genuine example of the proverbial political cliche: the stunning upset. Even on the day before the primary, Mahoney was considered a distant jongshot for the state's highest office.

Mahoney's victory demoralized and divided the Democrats in the general election, and liberals and moderates deserted him in droves. He ran on the slogan, "Your Home is Your Castle: Protect It," and his effort to fan racial fears over open housing angered many Democrats and cast an unexpected spotlight on the little known Republic candidate for governor: outgoing Baltimore County Executive Spiro T. Agnew.

Even then, he was "Spiro who?" but he became the progressive in the race - the man who seemed to stand, by comparison, for racial moderation in an era of riots and tension.

Agnew was elected in November 1966 and served less than two years before Richard Nixon, looking for a man with a progressive image who nevertheless took a hard line against civil disobedience, and a new face with a drive to campaign tirelessly, picked him as vice president.

And so Spiro T. Agnew became Maryland's first vice president and also the nation's first vice president to resign in disgrace for allegedly accepting cash kickbacks in white envelopes handed to him in his executive office building suite.

To be fair, the comparison between 1966 and 1978 wears thin in a number of ways. None of the Democrats has accused any of the Republican gubernatorial candidates of having the moral scruples of a Spiro Agnew, and racial issues in the present campaign have been muted, if present at all.

Moreover, Lee has had the advantage of more than a year of incumbency, whereas Finan never held the governorship. Burch does not exploit racial prejudice. Venetoulis lacks the stature of a congressman-at-large.

But in other respects, they were sufficiently similar in ideology and base of support to lead to direct comparisons with the 1966 race.

"It's eerie almost history repeating itself," said Jackie Smelkinson, who ran Sickles' headquarters office in 1966 and now manages Venetoulis' gubernatorial drive. "But I see Ted Venetoulis as a better candidate than Carlton Sickles."

Burch lacked the campaign funds and a strong political base in his drive for the State House. But his candidacy was taken seriously because he voiced many of the bitter frustations of conservative, blue-collar voters. Burch first ran for attorney general on Finan's ticket in 1966. His hard-hitting campaign style and angry outbursts against taxes, teachers, bureaucrats and political bosses reminded many observers of Mahoney's populist campaign.

"We all learned (from 1966) that a strong issue, no matter what side you're on, is the only thing that excites the electorate," said Burch's campaign manager Philip Altfield. "There was only one issue in 1966, 'Your Home Is Your Castle.'"

If Burch had remained in the race and pulled of an upset victory, he probably would not have suffered the Democratic rejections experienced by Mahoney. Burch is a long-standing party regular with support in the moderate, as well as conservative wings of the party, and is well-known in Democratic fundraising circles.

But his candidacy had enough fire power to fracture the party and give Republicans a helping hand in their campaign to recapture the State House. So if the GOP was looking with delight on the possibilities of another 1966, it joins the Burch supporters in disappointment over the attorney general's decision to drop out of the race.