Del. Wyatt D. Durrette Jr. of Fairfax, once considered the favorite for the Republican nomination for attorney general of Virginia, is now locked in a close contest with state Sen. J. Marshall Coleman of Staunton, candidates and party officials say.

Until about a month ago Durrette was thought certain to be the nominee because of greater support among Republican Assembly members, his highly-regarded campaign manager and his active cultivation of party conservatives.

But at meetings so far, Coleman has contended that Durrette once sponsored legislation authorizing collective bargaining for public employees, a bill removing the sales tax from food and non-prescription drugs, a general obligation bond issue in a year that Republican Gov. Mills E. Godwin opposed one and longer sessions and higher pay for legislators.

Durrette contends Coleman is misrepresenting his record. He said in an interview that his public employee legislation lacked key elements of collective bargaining and said he has since taken a position against all forms of public employee bargaining, including practices that would have been authorized by the bills he once sponsored.

The other positions cited by Coleman, Durrette said, do not in his view reflect on his moderate-conservative outlook.

"I was a leader of Youth for Goldwater when he was a leader of Young Southerners for Rockefeller in 1964," Durrette said.

Coleman, serving his first term in the Senate after three years in the House, stole a march on Durrette last fall by campaigning for Republican congressional candidates throughout the state while Durrette spent most of his time in the 10th District helpind Del. Vincent F. Callahan wage a lossing race for Congress.

Coleman's efforts earned him credit with both congressional candidates and their party supporters. He has followed up that phase of his campaign by aggressively contesting Durrette at city and county mass meetings held to select delegates to the state convention June 4. It is at this convention, rather than in a primary, that Republican nominees for statewide offices will be selected.

In addition to the surprisingly vigorous Durrette-Coleman race, there suddenly is a prospect for a close contest for the nomination for lieutenant governor.

Unhappiness among influential Republicans, including Godwin, over the unopposed candidacy of state Sen. A. Joe Canada, has brought Richmond investment banker Walter W. Craigie Jr. into the race. Craigie, former state secretary of finance, is putting together an organization of proven campaign officials and is expected to make a formal announcement this week.

The development of the two close contests has increased interest in the Republican convention.

Earlier this year, it looked to party officials as if their Roanoke meeting would be a somnolent affair devoted to suspenseless anointment of three candidates just as Democrats enter the final 10 days before their June 14 primary.

Lt. Gov. John N. Dalton still is certain to be the GOP nominee for governor - he has no opposition - but the spirited races to be his running mates are now being counted on by party officials to focus voter attention on the whole Republican slate.

Craigie described himself in an interview only as a "prospective candidate," but acknowledged that an experienced Republican campaign manager, Robert Weed, is already at work for him. Weed, has a winning record in closely contested Virginia campaigns. He managed the first two races of Fourth District Rep. Robert W. Daniel Jr. and last fall directed the successful First District campaign of Rep. Paul Trible.

Emergence of Craigie as a candidate ends weeks of searching by influential Republicans for competition for Canada. The Virginia Beach senator appeared headed for the nomination, until early February, when he cast the decisive vote in the Virginian Senate against ratification of the proposed Equal Rights Amendment to the U.S. Constitution.

Opposition to ERA would hardly have been a factor for the nomination but Canada in the past had declared his support of the amendment barring sex discrimination and his Senate vote was perceived as a broken promise.

Canada insisted his vote was consistent with his advocacy of an advisory referendum on ERA, but his conspicuous action focused attention of ERA advocates and foes on a potential GOP ticket member in a way that made Dalton supporters uneasy.

Ironically, out of 14 candidates seeking statewide office in both major parties this year, only Canada has a female campaign manager.

In recent weeks, Republican officials have privately reported that Godwin doesn't want to see Canada on the ticket partly because of opposition to him by Virginia Beach political figure Sidney S. Kellam, a long-time Godwon ally.

Craigie has attracted instant backing from such party conservatives as former state chairman Richard D. Obenshain and National Committee-woman Judy Peachee.

Craigie has been serving as chairman of the Dalton finance committee and is strongly persumed by party officials to be preferred by Dalton over Canada. A spokesman for the lieutenant governor, however, would say only that "he will be pleased to run with whomever the convention chooses."

Craigie made an appearance as a "prospective candidate" last week at an Alexandria Republican meeting - not one held for delegate selection - and now is expected to join Canada, Durrette and Coleman at almost nightly mass meetings in cities and counties the next seven weeks.

In the last presiedential election, Durrette and Canada both worked for nomination of Ronald Reagan while Craigie and Coleman supported former President Ford. Although Reagan was heavily favored by Virginia party regulars, all four candidates said in interviews that last year's presidential politics did not seem to be playing an important role in their races.