"I assure you that the opposition stands in one line and with a single heart. We are working toward the same goal," ElBaradei told skeptical reporters in a news conference on Wednesday.
The three main opposition leaders — ElBaradei, former Arab league chief and foreign minister Amr Moussa and leftist politician Hamdeen Sabahi — have little in common besides their opposition to what they see as a power grab by the Islamists.
There are other problems too with these three pillars of the opposition.
ElBardei lacks the charisma and oratorical skills needed to move crowds, at times sounding like an Ivy League professor.
Moussa is in his 80s and dismissed by many as a "relic" of the old regime with neither vision nor energy.
Sabahi, who finished an impressive third in the June presidential election, is the most charismatic of the three, with his leftist convictions appealing to many of the youths who engineered the uprising against Mubarak, but he is widely seen as a political rookie.
The strength shown by the opposition in recent days has impressed many, but questions linger about their future strategy.
"The opposition has proven stronger and more resilient than the Muslim Brotherhood expected," said Shadi Hamid of the Brookings Doha Center. "The question now is, what will they do with the momentum they have? The opposition has proven their ability to draw tens of thousands to the street but their ability to leverage this momentum into concessions is something else."