Ronald Reagan easily captured Virginia's 12 electoral votes, but Republican state Attorney General J. Marshall Coleman could prove the ultimate beneficiary of the GOP landslide and Democratic Lt. Gov. Charles S. (Chuck) Robb of McLean, the loser.

Coleman and Robb are to square off next year in a gubernatorial race that will be one of first tests of the durability of the Reagan majority. Many political leaders in the state said yesterday that if promises to be a contest in which Coleman now has a crucial asset: a well-organized and well-financed GOP machine that has dealt a decade-long series of electoral defeats to the battered Democrats.

"Everyone's sitting around here basking," said Anson Franklin, Coleman's chief political aide. "We're certainly starting with a good solid base for next year."

For the Democrats, Tuesday's sweeping defeat, which also cost them both of Northern Virginia's congressional seats, left few options. Even while talking gamely of rebuilding their party, Democrats marveled at the scope of the Republican triumph, which gave Ronald Reagan a 230,000-vote margin over Jimmy Carter in the state -- 10 times Gerald Ford's winning Virginia margin in 1976. The GOP also locked up nine of the state's 10 House seats

"It was like a runaway truck going through town too fast to get it number," said State Democratic Chairman Richard J. Davis, who along with Robb attempted to portray the results as more a national defeat than a state loss for the party.

"The issues next year will be different and the national economy and the inflation rate will not be a factor," said Robb, the party's only statewide officeholder. "I think there's a sense of rallying the troops and putting aside factional differences and a recognition that if the party can't get its act together, it's in for some lean years"

Besides Coleman, one of the other big winners in Tuesday's landside was Baptist preacher Jerry Falwell of Lynchblurg, whose Moral Majority Coalition claimed credit for registering 4 million new evangelical votes nationally who voted the conservative line.

"We thought we'd be instrumental in electing Ronald Reagan, but we had no idea we would win 40 out of the 43 state and national elections that our members worked in," said a jubilant Falwell, who came under heavy criticism in the campaign for injecting a new dimension of religion into politics.

Falwell also served notice that he and his supporters intend to play a major role in Virginia politics. He said he liked both Robb and Coleman but added that Moral Majority support of either candidate would depend on "which ones are willing to make the most concessions to our point of view."

Stunned Democrats, particularly those in Northern Virginia where Reagan's victory drove two incumbent liberal congressmen from office, groped for words yesterday in assessing the election and its impact on 1981.

"I think the people here and in the rest of the country just went in and voted, 'No,'" said Sue Hoffman, Carter's Northern Virginia coordinator. She was especially pained that the Carter backlash had cost the region the services of Democratic Reps. Herbert E. Harris and Joseph L. Fisher.

She said many of the Reagan voters were new-comers who "really didn't know their congressmen at all."

But there was disagreement over whether the "infuriated vote," as one state legislator called it, would carry over into next year's critical state and local elections.

"Democrats now have a record 14-year losing streak -- that's longer than any state Democratic party in the country," said Larry Sabato, a respected political analyst and political science professor at the University of Virginia. "The Democrats should realize that they are in desperate straits."

A recent Sabato poll showed Robb with a healthy 15 point lead over Coleman, but the pollster himself predicted the lead would prove tenuous once the real campaign begins next year. Robb, said Sabato, "has an awfully tough row to hoe. He will have to import some of the best national people to give him the campaign edge which his state party cannot give him."

Others were more optimistic. State Senate Majority Leader Hunter B. Andrews (D-Hamptio) said the party could recoup by next year "if we get together and discipline our party and ourselves. We've got to rebuild, and the legislative Democrats and the local Democrats are the only ones left who can do anything."

Andrews said the thrashing by Republicans -- "We got clobbered," he said -- had left a good many Democrats "rethinking" their plans to run for statewide office.

Democrats were particularily upset by their dismal showing in Northern Virginia, an area they must capture next year if their statewide candidates are to have any chance of success. "It's a grim picture," said Ann C. Broder, a longtime Democratic activist in Norther Virginia. "What's changed is that the traditionally safe, liberal precincts are no longer safe, and that's a big change from the way things have been here. I think we'll just have to go and lick our wounds and figure out what to do."

Sabato said he believed that Virginia Democrats could still come back next year if they nominate moderate candidates with suburban appeal. Carter, he said, ran only about 3 percent worse in Virginia than in the rest of the nation. He said Virginia "is not a land of lost causes per se. It's still a two-party state leading Republican."

But that tilt, said Northern Virginia's Hoffman, means the Democratic Party's work is cut out for it. And having a Republican now occupy the White House will be [TEXT OMITTED FROM SOURCE] she said.

"It would have been a lot nicer for us to have had a Democrat in there, even an unpopular one," said Hoffman.

Coleman aide Franklin agreed and could scarcely hide his delight over next year's prospects. "In the past, Republicans have been governor or lieutenant governor or attorney general, but we've never held all three at the same time," said Franklin. "Next year, maybe we'll change that.