The military for its part declared it was acting for "higher national interests" and vowed to crack down on any violence by any group unhappy with the electoral outcome.
At stake is whether or not Egypt will emerge from the instability of the 16-month transition that followed Mubarak's 2011 overthrow, or whether the power struggles will continue or even escalate to a more dangerous level. The Brotherhood has said repeatedly that it would not resort to violence, but several media outlets have launched a vigorous campaign against the movement claiming it will plunge the country into chaos if Morsi does not win.
Tensions soared Wednesday when the country's military-appointed election commission indefinitely delayed announcing the results of the weekend elections. The Brotherhood announced soon after polls closed Sunday that it had beaten rival candidate Ahmed Shafiq, an ex-air force commander who many view as the military's preferred candidate, by 52 percent to 48 percent. Shafiq has also claimed victory by a narrow margin.
Many accuse the military of planning to direct the election commission to announce a Shafiq win. Others say the commission has determined there was a genuine Shafiq victory but fears that no one will believe them. The commission itself says it is sorting out the claims of election violations filed by both candidates.
The Brotherhood has raised another possibility: Just before the vote, the nation's highest court dissolved the Brotherhood-led parliament and the military granted itself new exceptional powers, leaving the next president with limited authority. The generals won't let the commission announce Morsi's victory until they accept those decisions, some movement figures say.
"The military council is waging a psychological war and the delay in announcing the results is just part of it," said Saad Emara, a Brotherhood member of the disbanded parliament.
"They are holding the results to press the Brotherhood to accept [the military decision] as a de facto matter. As if saying, 'We are going to let the commission announce Morsi as a winner, in return for you shutting up and not talking about the constitutional declaration or the disbandment of parliament.' "
The Brotherhood sent its supporters to the streets for the fourth consecutive day to protest the military's power grab. On Friday, it was the biggest such rally, and protesters called on Morsi to be sworn in as president in Tahrir Square.