Richard D. Obenshain, a 42-year-old Richmond lawyer, came into yesterday's convention as the acknowledged front-runner among the four candidates.

He was presumed from the outset of the campaign to be the candidate to beat because of close ties to city and county party leaders established during his years as a GOP official.

Obenshain was reared on a farm near Blacksburg. Va. and graduated from Bridgewater College and New York Universary Law School.

He became active in Republican politics after moving to Richmond in 1960, when he was elected in absentia as chairman of the state Young Republicans while he and his wife, Helen, were on their honeymoon.

He ran unsuccessfully for Congress in 1964 and for state attorney general in 1969.

In 1972, he was elected state party chairman by conservatives dissatisfied with the party leadership of moderate Gov. Linwood Holton, one of Obenshain's opponents for the Senate nomination.

He resigned as state chairman in 1973 to become national GOP cochairman.

Obenshain is considered one of the architects of the coalition of Republicans, conservative Democrats and independents who have sustained Republican domination of statewide politics for the last 10 years.

In 1973, he played a prominent role in the move of former Gov. Mills E. Godwin from the Democratic to Republican Party. Last week, Godwin gave the Obenshain Senate candidacy a last-minute boost by endorsing him for the nomination.