AP Photo

After six months of political drama and wrangling, Lebanon has a government. Congratulations poured in from abroad as soon as cabinet proposals by the prime minister, Saad Hariri, won overwhelming parliamentary support.On a delicate visit to Washington, the president, Michel Suleiman, felt confident enough to promise a sceptical audience of US officials and Lebanese Americans that this national unity government would usher in a period of stability.

In fact, what happened between the elections in June and the formation of the new government was the political weakening of the March 14 coalition that nominally leads the cabinet, and the erosion of its tenets; from delineating borders with Syria to bringing suspects in the assassinations of anti-Syrian figures before an...