CAIRO -- Egypt's leading opposition group urged its followers Wednesday to vote against an Islamist-inspired draft constitution, ending weeks of indecision over whether antigovernment forces should boycott the referendum, which begins this weekend and pits secularists against the Muslim Brotherhood.
The move by the National Salvation Front is a crucial test of its popularity against President Mohammed Morsi and his Islamist supporters. The opposition movement has revived the country's revolutionary fervor but has been marred by divisions and poor organization, which are expected to be exploited by the Brotherhood's vast grassroots networks.
The National Salvation Front "decided to call upon the people to go to the polling stations and reject the draft by saying 'No,' " said Hamdeen Sabahi, a former presidential candidate and one of the group's leaders. "The people will rally at the polls and have a chance to topple the constitution." Perhaps sensing a possible setback, he added: "The referendum is not the end of our journey."
The Front said its decision was contingent upon judicial oversight, international monitors and increased security at polling stations. It is unclear whether those demands can be met. Many judges, angry at a recent power grab by Mr. Morsi that weakened the courts, have refused to supervise the referendum. That forced the Islamist leader to announce that voting would be held over two successive Saturdays -- beginning this weekend -- so participating judges can be rotated around the country.
A dialogue for national unity called for by the military between Mr. Morsi and different political factions was canceled Wednesday. The armed forces said few organizations agreed to attend. But the military, criticized for its harsh rule of the country after Hosni Mubarak was deposed last year, faced a backlash over perceptions that it was meddling in politics months after it had handed power to Mr. Morsi.
A political compromise appears increasingly elusive, as the president pushes ahead for the referendum and the opposition attempts to rally voters against a document that it fears will strengthen Islamist designs and jeopardize civil rights and freedom of expression.
That prospect was highlighted Wednesday, when a court sentenced Albert Saber, an atheist from a Christian family, to three years in prison for insulting Islam. He was charged with posting Internet links to "Innocence of Muslims," a film privately produced in California that denigrated the Prophet Muhammad and ignited anti-American protests around the Muslim world in September.
The country's latest crisis intensified in late November, when Mr. Morsi expanded his powers and freed his office from judicial oversight. The president has since offered concessions, but -- despite clashes that have killed at least eight people -- he has refused opposition demands to postpone the referendum until a document they find more representative is written.