Mohamed ElBaradei, a revolutionary favorite to lead post-Hosni Mubarak Egypt, backed out of his bid for the presidency Saturday, saying that the old regime was essentially still in place in the form of the ruling military council and that it was steering the country off the path to democracy.

The Nobel laureate and onetime head of the International Atomic Energy Agency returned to Egypt in the midst of last year’s 18-day uprising and quickly became a symbol of wisdom and leadership for many of the youthful revolutionaries leading the push to oust Mubarak. But he has failed to capture broad support, drawing criticism for his years spent abroad and accusations that he was trying to ride the revolution to power.

On Saturday, he said in a written statement and a video address posted on YouTube that the military rulers were taking Egypt in the wrong direction and that he could not participate in an election under their rule and with no constitution.

“The revolution’s ship has sailed a difficult path and was tossed and turned by high and treacherous waves,” he said in the statement. “It knows its way to safety, but the captain steering the ship — without the choice of its passengers and with no prior experience — has moved . . . among the waves without a clear compass.”

ElBaradei, who appeared dejected in the video, said in his statement that he and others had offered the military council help but that it had chosen to “move along the old path, as if a revolution never happened and a regime never collapsed.”

As the anniversary of the start of the revolt nears, many political activists worry that the council is seeking to preserve its political privileges to protect the military. Since the council assumed power in February, it has expanded the hated emergency law, made clear it wants to oversee the writing of the nation’s constitution and been accused of human rights abuses that rival Mubarak-era crimes.

Hala Mustafa, a political analyst and editor in chief of the Democracy Review Journal, said that ElBaradei’s decision represents a tacit rejection of a system still dominated by old government hands. In polls, Mubarak-era figures and rival candidates such as former foreign minister Amr Moussa and Mubarak’s last prime minister, Ahmed Shafiq, have been shown to be much more popular among Egyptians — and both are probably more acceptable to the ruling generals.

“Baradei saw himself being marginalized or eliminated,” Mustafa said. “His decision not to run is a veto of sorts of the current political process.”

In downtown Cairo, Shaima Hamdy, a young revolutionary, was demonstrating for the release of a journalist arrested by the military. Some 12,000 people have been arrested and prosecuted in hasty military trials, and as many as 100 people have been killed in security crackdowns. Hamdy said she had seen ElBaradei as the man who could change things.

“Baradei was my hope,” she said. “He should have continued.”

Nearby, Nafesa Zakaria Ayad, a tough-talking Egyptian-American lawyer, dismissed the news. She said ElBaradei’s bid was dead in the water and called his candidacy arrogant.

“No one was going to elect him. This way he kept his dignity,” she said. “I lived in America for 45 years and I wouldn’t come back to Egypt and say, ‘Hey, I’m going to be president.’ It’s not fair.”

ElBaradei turned down the post of interim prime minister in November because, his aides say, he was worried that the generals would treat him as a pawn. He has made frequent appearances in Tahrir Square and used his Twitter account to criticize the military leaders during security crackdowns in which unarmed protesters were beaten and shot.

By pulling out of the race, he has allied himself with the liberals and youth activists who have largely been sidelined in recent parliamentary elections. Islamists, dominated by the political wing of the Muslim Brotherhood, are expected to take about two-thirds of the lower house of Egypt’s first post-Mubarak parliament. Full results are expected this week.

ElBaradei said he would work with youth groups to bring them into the political fold from outside the system.

“I will be more effective if I do not, in light of these circumstances, run for any official position, including president, and focus my efforts on the big picture — how to hasten change and how to hasten the building of a new Egypt without restrictions, without chains,” he said.