It should come as no surprise that Saudi Arabia has come to the aid of Bahrain's royal family with about one thousand troops crossing the causeway between the two countries. If more troops are needed to ensure that the al-Khalifa regime does not fall, the Saudis will oblige. Put simply, Riyadh cannot tolerate Shiite domination of its offshore island, whether or not the al-Khalifas remain in power.

A Bahrain that is ruled by its Shiite majority is one-third of the ultimate nightmare for the Sunni rulers of the desert kingdom. The other two-thirds are a revolt by the Shiite majority in Saudi Arabia's oil-rich Eastern Province, which could spill over from the troubles in neighboring Bahrain and a massive influx of Yemenis, many of whom are adherents of the Zaidi branch of Islam, and have little in common with Saudi Wahhabism.

Stability in Bahrain is therefore crucial for the long-term future of the al-Saud family as rulers of their eponymous kingdom. Indeed, Saudi Arabia's rulers fully recognize that because memories in the Middle East are very long, the fact that the Hejaz was a separate Arabian kingdom as recently as the 1920s until it was conquered by Ibn Saud and merged with his kingdom of the Nejd means that the break-up of their country is hardly impossibility.

Other Gulf States, notably Kuwait, whose rulers are close to the al-Khalifa, may join the Saudi effort to stabilize Bahrain. So might the UAE, which shares Saudi fears of Iranian domination of the island, which was once an Iranian province, and which continues to smart over the Iranian seizure of its islands of Abu Musa and the Tunbs in 1971.

Washington cannot sit idly by as these events take place. The 5th Fleet is headquartered in Bahrain, as is the naval component of Central Command. The departure of the Navy from Bahrain would mark a signal victory for Iran, even, as is likely, the fleet were to find a new home elsewhere in the Gulf. Washington has no choice but to support the Saudi intervention.

Unfortunately, Washington appears to be willing to offer little more than words, and its words no longer carry much weight. The administration's vacillation over Libya, coupled with the imminent withdrawal of combat troops in Iraq -- where Prime Minister Nouri al-Maliki is becoming ever more authoritarian -- has underscored a growing perception of America's declining influence in the region.

Whatever happens in Bahrain will hardly change that perception. If, as is likely, the Saudis shore up the Bahraini regime, many will view the outcome as a victory for repression, and, given Qaddafi's recent successes against the rebels, a sign of the hollowness of American pronouncements about democracy. On the other hand, if some outside chance, the Bahraini regime falls to the Shiite opposition, the fruits of victory will be reaped by Tehran, not Washington, since one of the new government's first acts would be to expel the U.S. Navy.

One can therefore only conclude that, regardless of the outcome in Bahrain, the United States may be headed for even tougher times in the Middle East than those it has experienced in the past few years.