CAIRO — The presidential election commission confirmed the disqualification of three leading presidential candidates on Tuesday.

Citing narrow technical reasons, the commission kept on the sidelines the three most polarizing candidates: Omar Suleiman, the former spy chief under Hosni Mubarak; Hazem Salah Abu Ismail, an ultraconservative Islamist; and Khairat el-Shater, the candidate of the Muslim Brotherhood.

Mr. Shater was disqualified because of a criminal conviction in a political trial during Mr. Mubarak’s tenure as president, when the government was trying to check the Brotherhood’s power.

The Brotherhood swiftly endorsed a replacement nominee: Mohamed el- Morsi, the chairman of the group’s Freedom and Justice Party.

The step immediately vaults Mr. Morsi into the ranks of the front- runners because of the Brotherhood’s prestige and reach. The platform is unchanged: calls to reinforce Egypt’s Islamic identity, an emphasis on economic recovery, and business-friendly free-market economics.

He is considered less charismatic than Mr. Shater, but a more experienced politician. Mr. Morsi, an engineer, was a member of the Brotherhood’s parliamentary bloc under Mr. Mubarak.

Of the disqualified candidates, only Mr. Abu Ismail, the ultraconservative, vowed to continue to fight the decision. He campaigned on denunciations of American influence, but was disqualified because his mother had become an American citizen, putting him afoul of a no-foreign-parent rule his conservative allies had pressed for.

In a speech to hundreds of supporters gathered outside the commission offices, he called the documents showing his mother’s citizenship “a deception,” “fraud” and a “conspiracy.”

The disqualifications of Mr. Shater and Mr. Abu Ismail are likely to help the candidacy of Abdel Moneim Aboul Fotouh. He is a former leader of the Muslim Brotherhood and an internal reformer who was expelled for ignoring its promise not to field a presidential candidate, before the group itself dropped that pledge. He is running as a liberal Islamist, and has become the standard-bearer for more secular liberals as well.

Mr. Suleiman, 75, the former spy chief, was disqualified because he fell 31 short of the required 30,000 notarized statements of support to qualify as a candidate.

Mayy El Sheikh and Dina Salah Amer contributed reporting.(Copyright 2012 The New York Times Company 04/18/12)