(Reuters) - The race for Virginia attorney general could be headed for a recount as the preliminary vote tally on Wednesday showed the Democratic candidate with a razor-thin lead that could allow his Republican rival to call for an appeal.

Republican state Senator Mark Obenshain of Harrisonburg finished 541 votes behind Democratic state Senator Mark Herring of Leesburg out of 2.17 million cast in the Tuesday polls, according to unofficial state election board figures.

State law provides for an appeal of election results if the margin of victory is no more than 1 percent. Obenshain's margin is less than one-tenth that.

Obenshain said he would wait until the state election board completes its tabulations before deciding whether to seek a recount, a step he would be allowed by law to take after the election board meets on November 25 to formally tally and announce the results.

"We're going to wait until the State Board of Elections finishes its tabulations and make any further decisions at that time," Obenshain said of a possible recount in a statement.

A win by Obenshain would give the Republican party its only statewide victory in the 2013 election. Democrat Terry McAuliffe won the governor's race, and the lieutenant governorship went to state Senator Ralph Northam.

(Reporting by Ian Simpson; Editing by Scott Malone and Maureen Bavdek)