How did Washington become the best friend of the Muslim Brotherhood in Egypt, even as President Mohamed Morsi was asserting dictatorial powers and his followers were beating up secular liberals in the streets of Cairo? It's a question many Arabs are asking these days and it deserves an answer.

Morsi and his Brotherhood followers are on a power trip after decades of isolation and persecution. You could see that newfound status when Morsi visited the United Nations in September, and even more in the diplomacy that led to last month's cease-fire in Gaza, brokered by Morsi and Secretary of State Hillary Clinton. The Brotherhood leaders had gone from outcasts to superstars, and they were basking in the attention.

And let's be honest: The Obama administration has been Morsi's main enabler. American officials have worked closely with him on economic development and regional diplomacy. Visiting Washington last week, Morsi's top aides were touting their boss's close contacts with President Obama, and describing phone calls between the two leaders that led to the Gaza cease-fire.

Morsi's unlikely role as a peacemaker is the upside of the "cosmic wager" Obama has made on the Muslim Brotherhood. It illustrates why the administration was wise to keep its channels open over the past year of post-revolutionary jockeying in Egypt.

But power corrupts, and this is as true with the Muslim Brotherhood as with any other group that suddenly finds itself in the driver's seat after decades of ostracism. Probably thinking he had America's backing, Morsi overreached on Nov. 22 by declaring that his presidential decrees were not subject to judicial review. His followers claim he was trying to protect Egypt's revolution from judges appointed by Hosni Mubarak. But that rationale has worn thin as members of Morsi's government resigned in protest, thousands of demonstrators took the streets and, ominously, Muslim Brotherhood supporters began counterattacking with rocks, clubs and metal pipes.

Through this upheaval, the Obama administration has been oddly restrained. After the power grab, State Department spokesman Victoria Nuland said: "We call for calm and encourage all parties to work together and call for all Egyptians to resolve their differences over these important issues peacefully and through democratic dialogue."

Not exactly a thundering denunciation.

"You need you to explain to me why the U.S. reaction to Morsi's behavior is so muted," one Arab official wrote me. "So a Muslim Brotherhood leader becomes president of Egypt. He then swoops in with the most daring usurping of presidential powers since the Pharaohs, enough to make Mubarak look like a minor league autocrat in training by comparison, and the only response the USG can put out is (Nuland's statement)." This official wondered if the U.S. had lost its moral and political bearings in its enthusiasm to find new friends.

The administration's rejoinder is that this isn't about America. Egyptians and other Arabs are writing their history now, and they will have to live with the consequences. Moreover, the last thing secular protesters need is an American embrace. That's surely true, but it's crazy for America to appear to take sides against those who want a liberal, tolerant Egypt and for those who favor Shariah law. Somehow, that's where the Obama administration has ended up.

For a lesson in the dangers of falling in love with your client, look at Iraq: American officials, starting with President George W. Bush and Gen. David Petraeus, kept lauding Iraqi Prime Minister Nouri al-Maliki, despite warnings from many Iraqis that he was a conspiratorial politician who would end up siding with Iran. This misplaced affection continued into the Obama administration: Even after the Iraqi people in their wisdom voted in 2010 to dump Maliki, the United States helped him cobble together enough support to remain in power. Arabs observers are still scratching their heads trying to understand that one.

When assessing the turbulent events in the Arab world, we should remind ourselves that we're witnessing a revolution that may take decades to run its course. With the outcome so hard to predict, it's a mistake to make big bets on any particular player. The U.S. role should be to support the broad movement for change and economic development, and to keep lines open to whatever democratic governments emerge.

America will help the Arab world through this turmoil if it states clearly that U.S. policy is guided by its interests and values, not by transient alliances and friendships. If Morsi wants to be treated as a democratic leader, he will have to act like one.