Led by the lavish campaign of former Navy secretary John Warner, Republican candidates for the U.S. Senate in Virginia spent more than $900,000 in quest of the party's nomination according to the reports filed with the State Board of Elections.

Warner's spending total of $561,571 was a record for a convention campaign in Virginia.

Although he lost the Senate race to conservative Richard D. Obenshain, the political exposure that Warner got out of the race may not have been wasted.

Many Republican leaders expect him to be a candidate either for the U.S. Senate again in 1982 or for governor in 1981. Warner himself has said only that he remains "interested in elective politics" in the state.

The total spending by the four Republican candidates set a record for GOP nominating races, but is certain to be exceeded by the expenditures of the eight Democratic Senate candidates who sought their party's nomination at a separate convention. Final Democratic contribution and expenditure reports are due next week.

Warner's post-convention report showed that he borrowed $471,415 against his personal assets to finance most of his senate campaign.

Warner spent almost three times as much as Obershain, a Richmond lawyer. The GOP nominee listed expenditures of $193,926 and receipts of $195,307. About $20,000 of his contributions have come since he won the nomination.

Former Gov. Linwood Holton of McLean, who finished behind Warner in the convention balloting, reported spending $110,941 and receivng $114,297 in contributions. The fourth candidate in the GOP senate race, state Sen. Nathan H. Miller of Rockingham County, reported expenditures of $46,856 and receipts of $47,485. Miller reported loans by him $31,000 to his campaign.

Among those who contributed to Obenshain immediately after he won the nomination was Republican Gov. John N. Dalton, who gave the legal limit of $1,000.

Both before and after the nomination convention, Obenshain was the beneficiary of donations from conservative political committees, including the Conservative Victory Fund, the Committee for the Survival of a Free Congress and the National Conservative Political Action Committee.

The Republican Congressional Booster Club in the District of Columbia gave him the legal limit for a committee, $5,000 after he won the nomination.

Lawrence Lewis, the Richmond financier who has been a major fund raiser for Republican candidates during the recent ascendancy of the GOP in statewide elections, and his wife each have given Obenshain $1,000, according to the report.

Obenshain begins the general election campaign less well known than his Democratic opponent, former state attorney general Andrew P. Miller, but strong financial support from such conservative and Republican loyalists as Lewis is expected to help him close the name identification gap.

Among the post convention donors to the moderate Holton were Richmond retailers and philanthropists Sydney and Frances A. Lewis, who gave $1,000 each. The Lewises are the founders of Best Products Co. and in politics have been known mostly for their generous contributions to moderate and liberal Democrats, especially former Lt. Gov. Henry E. Howell.