The auditorium was smoke-filled and crowded; the drinks, bourbon and gin; the income level, six-figure; and the mood, confident as several hundred Republican bankers, lawyers, businessmen and their allies gathered Wednesday night in a local Holiday Inn.

They came to hear former Virginia governor Mills E. Godwin damn Jimmy Carter and the Democrats and to see their new prize, Sen. Harry F. Byrd Jr., who despite his formal status as an independent, is backing their GOP presidential ticket.

Most of all, they came to reaffirm that it is they who still wield political power in Virginia and that their candidate, Ronald Reagan, will be the latest in a growing list of Republicans to carry the state.

Their confidence should be no surprise in a state that, with the exception of the 1964 Goldwater debacle, has voted Republican in every presidential election since 1948. But just a few weeks ago, independent polls suggested Reagan had not nailed down his lead here and Democrats were talking about pouring in volunteers and money in an effort to pull what some called "a November surprise."

Last week that talk faded as two new surveys put Reagan ahead by a solid 10-point margin. By week's end, Republican leaders were flatly predicting Reagan would carry the state by 53 percent to 43 percent over Carter, with independent John Anderson drawing 4 percent of the vote. That would give the GOP a stunning victory that would be five times greater than Gerald Ford's narrow 1976 margin over Carter (51 percent to 49 percent). Virginia was the only southern state to back Ford then, giving him a 23,000-vote cushion.

"Two weeks ago, we were getting a little scared, quite frankly," says Alfred B. Cramer, Virginia GOP Chairman. "But things have been moving again, especially since the debate Tuesday night, and we feel the momentum has swung our way."

Independent analysts, although they disagree with the Republicans over the size of the margin, also believe the GOP is heading toward another Virginia victory this Tuesday. "I see Reagan scoring 50 percent or slightly over it, with Anderson getting around five points and carter taking the rest," says political scientist Larry Sabato of the University of Virginia.

Carter campaign officials gamely deny their man is fading, but even they are not predicting victory. Instead, they say the contest will be close. t

"The Republicans have constructed a big smokescreen," says Bill Albers, Carter state coordinator. "It's nip and tuck, and the final vote will be within 20,000 either way, much like '76."

One of Carter's biggest problems is Northern Virginia, where apparently his effort to win the support of federal workers is stumbling, just as it did four years ago. The president lost both the 8th and 10th Congressional Districts in 1976 by a four percentage -point-margin that was enough to cost him the state. His strategists had counted on his doing better with the area's civil servants, who Carter strategists believed would be just as wary of outsider Reagan this year as they were of outsider Carter in 1976.

But recent statewide surveys by Sabato, The Richmond Times-Dispatch and Republican pollster William Royall all show Carter trailing there by double-figure margins. Even Albers concedes: "We're down in Northern Virginia although we're doing all we can to turn it around."

Fairfax County Supervisor Audrey Moore (D-Annandale), a Carter supporter, says, "I talk to people and they all seem to be either voting for Reagan or for Anderson. It's surprising to me and I just can't explain it."

County Board Chairman John F. Herrity, a Republican, says flatly, "Reagan will do better here than Ford did. He'll score higher in the 8th and a little better in the 10th."

Besides dooming Carter's chances in the state, a Northern Virginia loss could rub off on the state's only two liberal Democratic incumbent members of Congress, Herbert E. Harris and Joseph L. Fisher, both of whom are locked in tight races with well-financed GOP opponents.

Campaign spokesmen for both Democrats concede they are concerned about Reagan's coattails but confidently predict they will overcome the problem.

"This is an extreme ticket-splitting situation, and so no matter how poorly Carter ends up doing, we think Herb will win," says Jane King, a spokesman for Harris. Many observers from both parties believe Harris will pull out a victory over GOP challenger Stanford Parris, the former incumbent whom Harris defeated in 1974 to take the seat.

Carter's prospective loss could have a greater impact on the more volatile 10th District, where Fisher apparently is running almost even with persistent challenger Frank Wolf. The Wolf campaign strategists say their most recent telephone poll of 307 likely voters, taken Thursday night, shows Carter trailing Reagan by 41 to 25 in the 10th, with 11 percent for Anderson and 23 percent undecided, with a 5 point margin of error.

"We think Reagan's going to kick the hell out of Carter in the 10th," says Richard Lobb of DCM Group, a political consulting firm advising Wolf. "It won't help Frank in the sense of people automatically voting a straight ticket, but we do think that the same people who decide they've had enough of Carter may also have had enough of a congressman like Joe who has supported Carter so faithfully."

The Fisher people note that their man won a solid victory in 1976 even while Carter was losing the district. "If that kind of ticket-splitting is as strong as I think it is, then we'll be in good shape," says Fisher spokesman Jean McDonald.

As for the state's eight other congressional districts, GOP incumbents are expected to coast to victory in five, while a sixth, Robert Daniel of Southeast Virginia's 4th District, faces a surprisingly tough challenge from longshot Democrat Cecil Jenkins, a Chesapeake city councilman. The Republicans are expected to easily take the formerly Democratic 3rd District seat in Richmond, where conservative Democratic Rep. David E. Satterfield is retiring.