Slogans calling on Mr. Morsi to leave or for his government to fall have energized crowds and drawn new faces to the opposition, including people staunchly opposed to Islamist leadership and those who have supported figures from Hosni Mubarak’s government, like Ahmed Shafik, a former minister who ran against Mr. Morsi in the presidential race. Strikingly, some revolutionary activists now refuse to use the word “remnant,” as they had in the past, to describe their new allies, saying instead that they are glad for the support of people who decided to stay home during the uprising.

It was unclear whether the newcomers would remain while the opposition pressed more concrete demands and stepped up its confrontation with the government. Sitting on a curb in Tahrir Square on Friday night, Adel Abdullah, an unemployed Web designer, said he was happy to find like-minded people also bitterly opposed to Mr. Morsi. But, short of demanding that Mr. Morsi leave office, he said he was not sure, practically, what the president’s opponents should do.

“The people don’t want him,” he said of Mr. Morsi. “I’m so glad he made a mistake.”

Other opposition figures were trying to find ways to capitalize on the president’s mistakes. Leaders of the newly formed National Salvation Front, a coalition of parties, threatened to call for a national strike and possibly to march on the presidential palace to prevent the draft constitution’s going to referendum.

Mohamed Ahmed, a leader of the April 6th Revolutionary Youth Group, spoke of plans to escalate the protests in an effort to win concessions on demands including a rescinding of Mr. Morsi’s edict; a new, more representative constituent assembly; and an overhaul of the Interior Ministry.