"Tis the season in Virginia for calls to party unity by the two U.S. Senate candidates and for efforts by each to exploit any disunity on the other side.

Disunity among Democrats has, in fact, played a major role in the election of senators and governors in Virginia since 1966, elections in which nary a Democrat has won.

This is a record that explains the slogan of Democratic Senate nominee Andrew P. Miller: "Getting together wins it."

Not only has Miller made party unity a campaign theme, he began with his acceptance speech to probe for fractures on the other side. He openly appealed for support from followers of former Republican Gov. Linwood Holton, a moderate, while calling the conservative GOP Senate nominee, Richard D. Obenshain, an "extremist."

Obenshain, for his part, has tried to perpetuate the division among Virginia Democrats by passing off Miller as a "liberal" who support Jimmy Carter and controversial former Lt. Gov. Henry E. Howell, who was defeated as the Democratic nominee for governor last year after beating Miller in the primary.

Despite these initial thrusts by the candidates, there is feeling among experienced political campaigners in Virginia that party divisions will not play the critical role in this race that they have in the recent past.

To become a decisive factor, they say, the disunity on the other side has to deprive the nominee of contributors and willing campaign workers he would have otherwise had.

More important, the disunity has to create doubts in the minds of independent voters. A candidate who is perceived as not fully accepted by his own party inevitably finds himself defensively explaining at problem to the independent electorate.

Howell was a classic case of a candidate saddled by party disarray, which his critics would say he caused. Without the support of the moderate-conservative wing of his party, he lost races for governor in 1973 and 1977. He was obliged in both campaigns to try to prove that he was not the dangerous liberal that his bitter opponents in the intraparty fighting painted him to be.

In 1969, Democratic gubernatorial nominee William C. Battle also fell victim to party divisions after beating conservative Fred Pollard and populist Howell in a fierce primary and runoff.

Holton became the first Republican governor of the century that year by masterfully exploiting the Democratic fractures. He managed on one had to convince many black and union political figures that he was a better alternative than the conservative who beat their champion, Howell. At the same time, he persuaded many conservative contributors to Pollard that they could not support a candidate whose liberalism had to be presumed from the fact that he served as President Kennedy's ambassador to Australia.

"It was an incredible political balancing act," says one of Holton's most influential supporters in the Virginia GOP.

Party disunity also was a major contributor to 1972 upset of former Democratic U.S. Sen. William B. Spong, even though the moderate Spong was himself a unifying figure among Democrats. Liberal presidential candidate George McGovern put such a strain on the Virginia party that year that it helped propel Republican William L. Scott into office.

Scott campaign manager Mike Donaldson viewed the disunity caused by the McGovern candidacy in Virginia during that campaign and confidently predicted a Scott victory to the disbelieving. Scott ran more than 16 points behind former President Nixon, but still collected a majority in the three-way Senate race.

The question is, are any of the ingredients of party disarray that affected all these recent campaigns present today? The answer seems to be no.

Holton and former Navy Secretary John Warner were Obenshain's leading opponents for the GOP nomination. Both have signed on as honorary co-chairman of his campaign and already have made their first, joint general election campaign appearance with him.

Equally important to the appearance of moderate-conservative unity behind Obenshain is the presence among his supporters of former Gov. Mills E. Godwin. A former Democrat, Godwin is a symbol to many independents who in his own, off-used phrase, "put principle above party." His endorsement put a stamp of acceptability on Obenshain that may help offset the Republican's partisan image among independent voters.

This lineup behind Obenshain will make it hard for Miller to paint the Republican as a polarizing figure, but the Democrat seems equally safe from such attacks.

He is not perceived in his own party as the "liberal" that Obenshain calls him, but the liberal wing of his party is not likely to desert him for a conservative Republican.

This is a state of affairs that many reduce the Senate race to a contest between two candidates debating pressing federal questions with little attention to the role of each in recent party politics.