Cairo (CNN) -- Barely a year after the revolt that toppled longtime strongman Hosni Mubarak, Egypt´s long-banned Muslim Brotherhood has become the leading force in the country´s new politics.

But that success is already leading to grumbles on the streets of Cairo that the world´s oldest and largest Islamist movement has become just another bunch of politicians, or worse.

"The lower house is with the Brotherhood. The upper house is with the Brotherhood. The constitutional council is with the Brotherhood. The presidency will be with the Brotherhood. The unions and professional associations are with the Brotherhood," Nasser Ibrahim, an archaeologist, told CNN. "It will be as if Mubarak´s party never left."

The Brotherhood announced over the weekend that its political arm, the Freedom and Justice Party, had nominated 62-year old multimillionaire businessman Khairat al-Shater as its candidate for president in May. Al-Shater is the party´s longtime second-in- command, a top strategist and financier.

It says its decision to enter the presidential race -- reversing repeated pledges to sit out the contest -- was made to maintain a smooth transition of power in Egypt, where a military junta took power after Mubarak´s ouster.

"We came by the vote of the people and by the choice of the people from within the system itself, so I think we are quite democratic in terms of the process and the means," said Jihad Haddad, who is helping organize al-Shater´s campaign. "What we really want is application of real reform policies on the ground, and we can´t have that opportunity if we are out of executive power."

The Brotherhood has as its stated aim the establishment of a more traditional Islamic society in Egypt. It was officially banned in Egypt under Mubarak but unofficially tolerated, though its members were periodically harassed and jailed.

With Mubarak gone, the Brotherhood claimed the lion´s share of seats in Egypt´s parliament and is expected to play a prominent role in the writing of a new constitution. But its decision to field a presidential candidate after all has hit a sour note in some quarters.

"We are surprised that the Muslim Brotherhood never keeps their word," said Ahmed Maher, founder of the April 6th Movement, one of the youth groups that led the uprising against Mubarak. "They said they would not seek more than 20% of parliament seats, and now they have the majority. Same with the president -- they specifically said they would not field a candidate and now they come with al-Shater."

Meanwhile, U.S.-based analyst Shibley Telhami said Freedom and Justice MPs he met with in Washington this week are already facing complaints from disgruntled Egyptians, even before they form a government of their own. He said one lawmaker told him, "I go back home to my constituents and they already are blaming me for a lack of action."

Sondos Asem, a spokeswoman for the Brotherhood, told CNN on Monday that the group decided to enter al-Shater in the May presidential vote because the rest of the roughly 450-member field lacks the "leadership potential that would bring about stability in Egypt and in our international relations."

"We believe there is some type of leadership vacuum among the current candidates, and we feel that we now have a historic responsibility to field the candidate who we believe will provide this kind of responsible leadership and who will safeguard the democratic process," she said. That process "is threatened by many attempts to dissolve the current parliament or to hinder the establishment of the current assembly," she said.

But Telhami, the Anwar Sadat professor for Peace and Development at the University of Maryland and a Brookings Institution scholar, said the decision to enter al-Shater is a risky move reflected in the leadership´s split vote on whether to nominate him.

Despite its dominance, the Muslim Brotherhood appeared to have been caught by surprise by the strong showing of the more conservative Salafist movement, which advocates the adoption of strict Islamic law. The Brotherhood has been most interested in keeping a strong hand on the writing of a new constitution, and it assumed that they could have enough influence on the presidency by endorsing another party´s candidate, Telhami said.

"They could back a liberal president who understands their interest and could make a deal with them," Telhami said. "But things didn´t work out the way they envisioned, in part because they didn´t expect how tough the attack from the right was going to be."

The Brotherhood was late to join the protests that toppled Mubarak, and the liberals and secularists who led that uprising fear that it may use its electoral victories to impose a fundamentalist Islamic agenda. While considered a conservative, al-Shater is also credited with being the driving force behind the Brotherhood´s affirmation that Egypt should continue to honor its international agreements -- including its peace treaty with Israel.

Haddad said that if the Brotherhood wins the presidency, "We will be accountable for everything." But Cairo businessman Usama Hassan complained that the Brotherhood remains far too secretive.

"There is no transparency, and since there is no transparency, we are still in the reign of Hosni Mubarak," Hassan said.

And Islam Lotfy, a former leader of the Brotherhood´s youth movement, says he was kicked out of his job at al-Shater´s orders for trying to set up a centrist party after the revolution.

"I believe Khairat al-Shater likes everything concentrated around him," Lotfy said. "He holds all the threads in his hands -- the threads of politics, money and missionary work -- and that is very worrying."

He said Egypt may find itself with another strongman in the mold of Gamal Nasser, who founded the modern state, "but with the beard of Ahmadinejad."

In recent weeks, the group has clashed with the Supreme Council of the Armed Forces and the civilian government the generals installed, led by Mubarak-era Prime Minister Kamal Ganzouri. But Alaa al-Aswani, a liberal novelist and commentator, says it has played into the hands of the generals.

"The Muslim Brotherhood has been used as a tool by the SCAF to stop the real change, just to make a change on the top, on the surface, in order to change the revolution into a coup d´etat," al-Aswani said.

Others see its entry into the presidential race as a way to secure its position in the face of gains from the Salafists, who took the second-largest share of seats in parliament.

"The Muslim Brotherhood, like the former NDP, are only concerned with their self-interest," Maher said. "We see this by their refusal to participate in major protests or events. They failed to join the revolutionary voice against the current Ganzouri government and boycotted protests when he was first instated, and now they are fighting and challenging SCAF to expel him when he did not serve their interests." CNN´s Matt Smith in Atlanta contributed to this report. (© 2012 Cable News Network 04/05/12)