“The legitimacy of the regime is on the verge” of collapsing, ElBaradei said.

ElBaradei said one person had been killed, but there was no official confirmation of a death. The Ministry of Health said at least 211 had been injured. Another 32 had been arrested, according to the Interior Ministry.

Morsi remained silent, and it was unknown if he was in the palace during the violence.

In Washington, the Obama administration called for dialogue. White House spokesman Jay Carney said that the administration was looking for the Egyptian government to show restraint and for both sides to refrain from violence.

"We remain concerned with the continuing lack of consensus regarding the recent constitutional declarations and the handling of the draft constitution in Egypt,” Carney said.

At NATO, Secretary of State Hillary Clinton told reporters that dialogue is “urgently needed.”

But the violence Wednesday, the latest in what has become nearly daily protests, made such an outcome less likely. Like Republicans and Democrats during the 2012 election, both sides disagree on facts, making talk of resolution even more difficult.

A day earlier, anti-Morsi protesters massed at the palace, but the Muslim Brotherhood’s newspaper on its front page Wednesday showed only a photo of a single demonstrator smashing a car, suggesting that only a few turned out and that those who did were violent. Meanwhile, more liberal papers showed wide shots of thousands gathered at both the palace and at Cairo’s Tahrir Square, the site of the 2011 uprising.

The Muslim Brotherhood’s newspaper called the protesters “anarchists,” while describing the constitution as a document designed to protect the poor and marginalized. More liberal publications describe the constitution as vague and a threat on basic freedoms.

There was even disagreement on how many judges had said they would help oversee the Dec. 15 referendum. Liberal papers said only 200 judges had volunteered, while the Brotherhood said that thousands had called off a strike and would be on duty for the voting.

“In a crisis facts are in short supply, and we are in a crisis. Some of these things are indeterminate,” Feldman said. In addition, “there is general uncertainty not only about what opponents will do, but what your side will do.”

Which side will prevail remains unclear. A poll released Wednesday by the Egyptian Center for Public Opinion Research, conducted Nov. 28-29 of 2,008 Egyptians, found that 30 percent support Morsi’s constitutional decree; 37 percent oppose it; and 33 percent are undecided.

Special correspondent Amina Ismail in Cairo contributed to this report.