"The Senate Republicans are now the majority party in the Senate of Virginia," Republican Senate leader Tommy Norment said in a statement.
However, The Washington Post reported with Republican challenger Bryce Reeves out-polling Democratic incumbent R. Edward Houck by 86 votes and provisional ballots yet to be counted in their 17th District south of Fredericksburg, a recount was possible. That would leave control of the Senate in doubt.
Senate Majority Leader Richard Saslaw told the Post Wednesday Democrats would press on, despite acknowledging it doesn't look good for the party.
"I don't hold out much hope," Saslaw said. "You go through a lot of what ifs."
The Republicans needed to oust two Democrats in Tuesday's elections to win an effective majority in the Senate.
If Houck were to lose, the Senate will be evenly split, with Bill Bolling, the Republican lieutenant governor, casting tie-breaking votes.
Gov. Robert McDonnell said the Republicans added significantly to their already large margin in the House of Delegates.