Virginia's delegates to the Republican National Convention went home last weekend united behind their party's nominees for the White House, Ronald Reagan and George Bush. But when the focus turned to state rather than national politics, there were deep splits in the delegation that could influence the outcome of future GOP campaigns.

The moderate-conservative wing of the state Republican Party, epitomized by Gov. John N. Dalton and Attorney General J. Marshall Coleman, was clearly out of step with ultraconservative, hard-core Reaganites, led by Fairfax lawyer Guy O. Farley Jr. and Reagan's state campaign chairman, John alderson.

More importantly, the moderates were outnumbered.

The clearest indication of the split came on the opening day of the convention, when "pure Reaganites showed their preference for conservative congressman Jack Kemp of New York as the vice presidential nominee.

In a straw poll, Virginia delegates picked Kemp 31 to 10 over George Bush, the first choice of party leaders such as Dalton, Coleman, state Republican chairman Alfred Cramer and U.S. Rep. Paul S. Trible of Newport News. Cramer and Trible, after pressure from Reagan supporters, later switched their allegiance to Kemp, a move that left some of the Bush people privately disgusted.

But the real game being played here was not Kemp versus Bush, but rather a contest for control of the state party, and for power to name GOP nominees for state office next year and the U.S. Senate in 1982.

Coleman is the runaway favorite for the gubernatorial nomination, but among Reagan supporters his devotion to the conservative line is highly suspect. Several talked quietly last week of mounting a challenge to his nomination next year, but so far they have not found an attractive alternative candidate.

One figure may have emerged last week: Farley, the highly ambitious former Democrat who led the move that resulted in the anti-ERA and anti-abortion planks in the GOP platform and then launched the spirited drive to convince Reagan to name Kemp as his running mate.

"Guy proved to be a good leader in a convention situation, and that's got to be important for next year," said Del. Lawrence Pratt of Fairfax, a Farley ally.

Most observers expect Farley, who for six years in the 1960s served as a Democratic representative to the General Assembly, to try for lieutenant governor next year. There are a few who believe he may go all the way and challenge Coleman.

Farley's base of support consists of the new evangelicals who have flocked to the Republican Party this year to nominate Reagan and to promote "family issues" such as their opposition to the ERA and abortion.

Those just happen to be two issues where, in their eyes, the flamboyant Coleman is vulnerable. Coleman supports ERA, which most mainstream Republicans in Virginia do not, and while he is careful not to appear "pro-abortion," he does not support a constitutional amendment banning abortion, as called for in the Republican platform.

Farley also has built strong ties with Helen Obenshain, Virginia's new national committeewoman, whose soft-spoken influence on the conservative wing of the party is not to be underestimated. Obenshain is the widow of state party chairman Richard Obenshain, who was the GOP's 1978 U.S. Senate nominee until his death in a plane crash that year.

Coleman's people believe Farley is too new and too unknown to mount a credible challenge to their man. They also profess not to be worried about Coleman's apparent unpopularity with a sizable segment of the delegates who came to Detroit.

When delegates Jade West and Raymond LaJeuness, both of Arlingotn, publicly criticized Coleman last week for being "too liberal," he shrugged it off, noting that in the last election he defeated a Democrat considered even more conservative than he.

But the criticism and the talk of dissatisfaction clearly took its toll on Coleman, who kept an unusually low profile during the four-day convention. Normally a lively man who makes the most of media contacts, Coleman was so circumspect in his public comments that many reporters gave up asking him serious questions.

"You know I'm not a controversial person," said the usually self-confident, and controversial, attorney general as he flashed a smile to the press.