State Sen. Richard H. Black has made the surprise decision not to run for the seat of retiring U.S. Rep. Frank Wolf, helping Republicans avoid a contentious nomination fight that could have highlighted splits within the party.

On Monday, Black (Loudoun) officially launched his campaign to succeed his fellow Republican Wolf in a competitive district that stretches from McLean to the Shenandoah Valley. That put him on a collision course for the GOP nod with Del. Barbara Comstock (Fairfax) and Frederick County Board of Supervisors chairman Richard C. Shickle.

Two days later, Black abruptly reversed course, releasing a statement to the conservative Bull Elephant blog explaining that he had decided to stay in the Senate.

“I seriously considered running for the 10th Congressional seat, however, after meeting with Republican Caucus leaders in Richmond, it is imperative that I remain in the Senate where I am needed to maintain our 20/20 split,” Black said, according to the statement.

Black did not respond to a request for further comment on his decision.

Black’s move came a day after Republicans failed to capture the open Loudoun-based Senate seat of Attorney General Mark Herring (D). Democrat Jennifer Wexton’s victory Tuesday in a special election put Democrats on course to take control of the Senate if they can also prevail in next week’s recount of the race to replace Lt. Gov. Ralph Northam (D). Northam would serve as the tiebreaker in a 20-20 Senate.

Black has a committed core of conservative followers who revere him for his stances on issues like abortion and gay rights. But he also has a history of controversial comments that made Republican leaders worry he would have trouble winning a general election, and much of the party establishment would prefer that Comstock win the nomination.

Republican officials in the 10th District are set to meet Thursday to decide whether to hold a convention or a primary to select their nominee.

On the Democratic side, Fairfax County Board of Supervisors member John Foust is seen as the frontrunner for the party nomination. Fairfax lawyer Richard Bolger, Leesburg architect Sam Kubba and Marine Corps veteran David R. Wroblewski are also running. Karen Schultz, a professor at Shenandoah University, has said she is considering a run as well.