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While analysts ask who or what is behind the sustained protests in Egypt, one group is now seeking political legitimacy.

Technically banned under Egypt's constitution that forbids religious based parties, the Muslim Brotherhood is now throwing its support behind Mohammed el Baradei as an opposition leader.

But many fear that if Egyptian President Hosni Mubarak goes, the real replacement will be either the Muslim Brotherhood itself, or an Islamic fundamentalist group. El Baradei insisted on Sunday talk shows that the fear was unwarranted.

“This is total bogus that the Muslim Brotherhood are religiously conservative,” El Baradei told ABC’s “This Week.” “They are no way extremists. They are no way using violence.”

But critics point out that the Brotherhood, which was established in Egypt in the 1920's, is synonymous with political Islam which supports the use of Islamic law known as Sharia.

“Right now the Arab Republic of Egypt does not impose Islamic law in its fullness,” Rob Spencer, the head of Jihad Watch told FOX News. “The Muslim Brotherhood wants to change that.”

Among the brotherhood's graduates: Al Qaeda's number two leader, the Egyptian doctor Ayman al-Zawahiri who was imprisoned for three years on weapons charges following President Anwar Sadat's assassination in 1981, Hamas, the terror network behind suicide bombings and rocket attacks in Israel, and the Islamic Jihad Movement in Palestine, whose goal is the destruction of Israel.

Walid Phares, who is a terrorism analyst for FOX News, has studied the Muslim Brotherhood. Phares says its history shows that the group is not secular and not moderate.

“The Muslim Brotherhood is the mothership for the jihadi ideologies and thinking. And therefore one can say today's Al Qaeda, and today many other jihadists, are off shoots of the Muslim Brotherhood.”

Other analysts, including Michael O’Hanlon of the Brookings Institution argue that it may be impossible for the United States to resist dealing with the Brotherhood as a player in Egypt.

"It's not out there in the business of committing terrorist actions,” O’Hanlon pointed out. “Now, the question is -- the question is what lurks beneath, ideologically and otherwise."

Analysts agree that the demonstrations are creating an opening for the Muslim Brotherhood to establish itself as a viable opposition, but the impact reaches beyond Egypt with ramifications for Israel, the United States and its allies. As one analyst said, Iran could end up being the big winner.