For incumbents on the Fairfax County Board of Supervisors, the Dulles rail issue could not have come to a head at a worse time.

With all 10 members up for election in November, the course of the mammoth rail extension is threatening to turn into a political liability for those running for another term. Supervisors are now faced with deciding whether to fund the project with an unpopular aerial rail through Tysons Corner, or withhold $400 million in order to pressure the state to build a tunnel under Tysons and put the entire 23-mile project out to bid.