In a reflection of the complex nuances at play, Sabahi refused to describe the current conflict roiling Egypt as a clash between secularism and theocracy, saying that in the Arab world, religion and public life could never be distinct in accordance with the Western model.
Rather, he said, the issue was preventing the Brotherhood from establishing a "tyranny" as a political movement not unlike that of the previous authoritarian regime.
He likened Morsi to the ousted leader, Mubarak, saying the Brotherhood is after absolute power.
"He (Morsi) reached power democratically, but is not exercising power democratically," he said, adding that the Brotherhood "wants to establish a system of tyranny in their benefit."
Regarding the fears of theocracy, Sabahi said, "We are against separation of religion and state ... The intellect of the Arab region, and Egypt, is built essentially on religion and specifically the Islamic religion."
Nonetheless, Sabahi said the opposition would continue to fight the constitution, arguing that the low turnout made it illegitimate.
"From the beginning the National Salvation Front said this constitution does not represent the people," he said. "This constitution is not one of national consensus, but of national division."
He said the NSF would now try to remain united in preparation for possible participation in the upcoming parliamentary elections.
He said the front has no immediate plans to unite under one party, but that as a coalition they could win a majority of seats if electoral laws mandated an end to political proselytizing in mosques and placed a limit on the funds used for political campaigns.
Another key issue for the opposition has been enabling people to vote outside their home district. The absence of this has aided the Islamists, who have the money to bus supporters back home to vote. The opposition, though, has also warned that rigging could be made easier if people vote from any location and point to the current use of Brotherhood-manned buses to transport poor voters.
"I am sure that the non-Islamists are the real majority in Egypt. But the Muslim Brotherhood enjoys strong organization, and the forces that oppose them do not have the same organization or finances," he said.
The Brotherhood emerged as the country's strongest political force after the popular uprising that toppled Mubarak nearly two years ago. They won the most seats in parliament, before it was dissolved by the courts, and won the presidency. Liberal and secular groups have consistently failed to beat the Brotherhood at the polls since.
That was until Sabahi, a charismatic populist, appeared as a surprise presidential contender against Morsi and his rival, Ahmed Shafiq, Mubarak's last prime minister, an ex-military man who lured voters with promises of stability.
Sabahi had a last-minute surge after campaigning on promises to help the poor and harkening back to the nationalist, socialist ideology of Gamel Abdel-Nasser, Egypt's president from 1956 to 1970.
Would Sabahi — known as a fervent opponent of Israel — cancel the landmark 1979 peace treaty if he one day ascended to power?
No, he said. The main issues facing Egypt today are resolving internal problems, especially endemic poverty — and he would not risk that priority issue by courting war with a neighbor.
In contrast to the Brotherhood, which has several offices in every Egyptian governorate, Sabahi spoke from the office of a famous Egyptian movie director, who lent him the space.
"The Brotherhood is losing every day. Mohammed Morsi is losing every day," Sabahi insisted, sitting among black and white pictures of Egyptian cinema actors emblematic of the 1960s — a time of resurgent Arab nationalism less complicated by the politics of religion.
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