AMMAN, Jordan — That one of the most overt challenges yet to the authority of Jordan’s king took the form of a song-and-dance routine speaks to the restraint with which the Arab Spring has unfolded here over the past 16 months.

The identity of the participants and the words they sang, immortalized in a video posted on YouTube, underscored just how dangerous the discontent pulsing through this little kingdom could become.

“Ali Baba the Second and his 40 thieves,” the men intoned rhythmically as they danced the traditional “dabka” at a busy traffic circle in central Amman, in what was unmistakably a direct reference to King Abdullah ll. “The people are fed up, the security forces are fed up, and the riot police are fed up.”

The men who were singing were native Jordanians, “East Bankers” who belong to the tribes from which most members of the army and security forces are drawn, and whose loyalty to the monarchy has never been in question — until now.

“We are loyal to the country, but not exactly to the king,” explained Munzer Ali, a retired policeman who was among those who participated in the protest in March. “If the regime was good, we would be loyal. But it is not. It is corrupt.”

Amid the bloodshed in neighboring Syria and the drama of the revolutions in Tunisia, Egypt and Libya, the relatively low-key unrest simmering in Jordan has largely been ignored. Protests demanding political reforms, but not the fall of the monarchy, are small and generally well-behaved, and security forces have mostly refrained from using force to suppress them.

But the civility masks deep and growing tensions that call into question the stability of this strategically significant kingdom of 6 million people, a bedrock of U.S. influence in the region and Israel’s last reliable Arab ally since the fall of Egypt’s Hosni Mubarak.

A slumping economy and a string of corruption scandals involving ministers and members of the king’s inner circle have heightened resentment of the ruling elites. Journalist Jamal al-Muhtaseb was detained last month and charged with jeopardizing state security for reporting on one scandal, a housing project for the poor in which hundreds of millions of dollars are allegedly missing.

Frustrations that reforms promised last year have not been implemented intensified in recent days after the king replaced his prime minister for the fourth time in just over a year, a move widely viewed as another delaying tactic.

Criticism of the king, long a taboo potentially punishable by death, is becoming more vocal and direct, establishing a worrying new trend for the Hashemite family that has ruled Jordan since 1946.

“It is public criticism. It’s clear and it’s candid, and that never existed in Jordan before,” said Zaki Saad, a leading figure with the Islamic Action Front, the political party of the Muslim Brotherhood, Jordan’s most organized opposition movement.

“This is unprecedented, and the only way out for the king is to move toward real reform. If he doesn’t do this, he will be in trouble.”