CAIRO—Thousands of mostly Islamist protesters flooded into Egypt´s capital Friday in a show of force aimed at pushing Egypt´s military leaders to block presidential candidates who held leading positions in the country´s ousted regime.

The march came one day after the Islamist-dominated Parliament passed a so-called isolation bill that, if passed by the ruling military council and upheld by Egypt´s courts, would prevent Omar Suleiman, a former intelligence chief and briefly vice president, and Ahmed Shafiq, a former prime minister, from running in presidential elections that begin on May 23.

The march and parliamentary legislation are the latest salvos in a confrontation between Egypt´s Muslim Brotherhood and the interim ruling military council. While Mr. Suleiman has repeatedly denied that he is the military´s choice for Egypt´s presidency, the "isolation" bill challenges the ruling council of generals to demonstrate its commitment to a revolution it has often claimed to protect.

"If Tantawi does not pass the law, we will all go down in the streets to protect the ballet boxes," said Abdel Hakim Hindawy, a protester who said he served a 10-year jail sentence under the former regime simply for "wearing a white gown and a long beard." Mr. Hindawy was referring to Field Marshal Hussein Tantawi, the head of the ruling Supreme Council of the Armed Forces and Egypt´s acting head of state.

"That´s how we will guarantee that there won´t be any fraud, and Egyptians won´t vote for regime remnants," he said.

Despite the ubiquity of long beards, white robes and full face- covering niqab veils that signify the most conservative Islamic ideologies, the chants and speeches emanating from the Muslim Brotherhood´s soundstage on Friday were deliberately non-Islamist.

Most of the Muslim Brotherhood-aligned demonstrators focused their rage on Mr. Suleiman´s cozy relationship with Israel. As the powerful intelligence chief for former President Hosni Mubarak, Mr. Suleiman was known as the steward of Egypt´s unpopular peace treaty with the Jewish state.

"Suleiman, be ashamed of yourself, you are an ally of Tel Aviv!" went one of the chants.

On the Muslim Brotherhood side, the calls of "Islamic! Islamic!" and demands for Islamic law that have characterized past rallies were largely absent.

The choice of secular-oriented signs and slogans may have been a retort to Mr. Suleiman´s claims, published in the Egyptian press on Thursday, that Islamist politicians have "hijacked" Egypt´s revolution.

Instead, Brotherhood speakers praised the assembled masses for creating a rare moment of political unity against Mr. Suleiman and the military leadership.

But as half of the crowd condemned Mr. Suleiman´s presidential bid, another soundstage set up by supporters of Hazem Salah Abu Ismail, a lawyer turned Islamist preacher, condemned the military leadership for allegedly conspiring to exclude Mr. Abu Ismail from the race.

Mr. Abu Ismail could be barred from the elections because of his mother´s alleged American citizenship. A constitutional declaration passed by the military last year forbids candidates from running for president if one of their parents holds citizenship in another country.

Mr. Abu Ismail´s supporters, who include many among the vast ranks of hard-line Salafi Islamists, shouted slogans calling for "jihad" or religious struggle against government corruption.

The commission will publish a preliminary list of approved candidates Saturday—preparing the ground for an explosive confrontation between Mr. Abu Ismail´s supporters and the ruling military regime.

In another blow to the purported unity wrought by Friday´s march, the liberal protesters whose activism laid the groundwork for last year´s revolution didn´t participate.

The April 6 Youth Movement, one of the leading activist groups, said on its website that Friday´s march amounted to a political power play by "some actors in the political scene"—a veiled reference to the Islamist politicians who dominate Egypt´s Parliament.

But many of the Islamist participants on Friday said they hoped to join next week´s march as well—a commitment that, if fulfilled, could help unite Egypt´s polarized political scene against the military leadership. (Copyright © Dow Jones & Company, Inc.) 04/14/12)