CAIRO — An Egyptian court on Wednesday unexpectedly declined to disqualify for the moment an ultraconservative Islamist from running for president because of his mother’s status as an American citizen.

The candidate, Hazem Salah Abu Ismail, is a front-runner in the polls and is known for denouncing American influence over Egypt. But his eligibility to run is in question because Egyptian law prohibits candidates with at least one parent who held foreign citizenship. Before she died in the past few years, Mr. Abu Ismail’s mother had become an American citizen, traveling with a United States passport and registering to vote in Los Angeles.

Late on Wednesday, however, a court ruled in Mr. Abu Ismail’s favor in a lawsuit he had filed demanding that the Interior Ministry prove his mother had become an American citizen. The ministry was unable to produce any official Egyptian documents confirming that.

By midnight, Mr. Abu Ismail’s supporters were celebrating in the streets. Still, the ruling on Wednesday did little to settle the issue. The national election commission will make the final determination of his eligibility, and it could disqualify him based on the ample American documentation of the mother’s citizenship.

If Mr. Abu Ismail is disqualified, his exit from the race would benefit the two more moderate Islamist candidates: Khairat el-Shater of the Muslim Brotherhood, and Abdel Moneim Aboul Fotouh, a liberal former Brotherhood leader. (Copyright 2012 The New York Times Company 04/12/12)