"They spent more than one year and a half waiting for what will happen in Syria because they feel if Muslim Brothers there reach power, this will empower them by default."

The Brotherhood says it is watching the Syrian conflict, but not taking an active part in it. Nimer al-Assaf says the group’s leaders do not send warriors to fight, although he argues it is their right.

It is not clear what the long-term goals of the Brotherhood are in Jordan. The group has refused discussions with the United States and Israel. Yet, the Jordanian government honors a peace treaty with Israel. Mr. Assaf admits this would change should the Brotherhood become a leading political player.

"Things become different. You have to deal with the world, whether you like them or not."

He says any changes might come through a special nationwide vote.

Opponents of the Brotherhood see the rise of Islamists in Jordan and across the Middle East as a hijacking of the hopes and goals of the Arab Spring. Mister al-Rantawi believes that wealthy conservatives in Saudi Arabia and Qatar are to blame. But the group dismisses such criticism, linking its rise to the expression of popular will.

In Egypt, the Muslim Brotherhood came to power following the ouster of longtime leader Hosni Mubarak. The group’s presidential candidate, Mohamed Morsi, took office earlier this year.

This week, Egypt revisited protests similar to those almost two years ago. Tanks were deployed to the presidential palace in Cairo following deadly clashes between supporters and opponents of Mr. Morsi.