Barack Obama has been fortunate in the Middle East so far. Yes, his attempt to revive the Israeli-Palestinian peace process has been a high-profile failure. But Israel, the Palestinians and the region as a whole have enjoyed a remarkable stretch of relative tranquility and stability during the past two years.

This week has brought signs that that luck may be about to change. If it does, it will not be because Israelis and Palestinians have not agreed on a two-state solution. Rather, it will be because the regional troubles that the Obama administration has ignored in its preocupation with the peace process can no longer be contained.

The most obvious symptom of that is in Lebanon, where the Hezbollah movement caused the collapse of the unwieldy "unity" government Wednesday even as its pro-Western prime minister, Saad Hariri, was meeting with Obama at the White House. Lebanon is a prime front in the regional cold war between Iran, Syria and their militarized proxies, including Hezbollah and Hamas, and the "moderate" and mostly Sunni U.S. allies.

An eruption of actual civil war in Lebanon does not seem to be imminent, in spite of the likelihood that an international tribunal will soon indict members of Hezbollah for the murder of Hariri's father. But what the militia's move vividly demonstrated is that the Iranian side retains the initiative. Because Hamas and Hezbollah are the two strongest military forces in the Levant other than Israel, they have the capacity to provoke, to disrupt and to start an armed conflict at any time of their - or Tehran's - choosing.

Obama's approach has been to mostly ignore that threat while focusing on peace diplomacy, in the hope that a breakthrough would undermine the political appeal of Hamas and Hezbollah. But now both Iranian allies are flexing their muscles. Since the beginning of January, according to Israeli officials, more than 20 rockets and mortars have been fired from the Gaza Strip at Israel, renewing the bombardment that led to Israel's 2008 invasion of the territory.

On Thursday, following a tough warning from Egypt that it was risking another war, Hamas deployed security forces to enforce a cease-fire. But Israeli accounts say Hamas and Hezbollah have spent the past several years stockpiling tens of thousands of missiles, including scores that could reach Tel Aviv; the chances that the region will survive another year without their use are looking slimmer.

The most imminent threat to U.S. interests in the Middle East, however, is not war; it is revolution. Last month in the obscure Tunisian city of Sidi Bouzid, a desperate man set himself on fire after police confiscated his unlicensed vegetable cart. This spark touched off what has now become a conflagration of daily protest demonstrations that threatens to consume the 29-year-old dictatorship of Tunisian President Zine el-Abidine Ben Ali - and spread to the other rotting Arab autocracies that line the south shore of the Mediterranean.

The violence has already migrated to Algeria, and Arab media are full of speculation of where the "Tunisia scenario" will appear next: Egypt? Jordan? Libya? All those countries are threatened by rapidly rising global prices for food and fuel; the United Nations warned last week of a "food price shock." All have large numbers of restless, unemployed youth. And all are governed by repressive regimes that not only have refused to embrace political reforms in the past decade but have cracked down harder on domestic opponents since Obama took office. It's hard not to attribute that trend at least in part to the administration's relaxed attitude toward reform and its reluctance to defend human rights and democracy.

In that sense, the only good news this week has been the signs that the administration is finally changing course. In a tour of several Arab nations, Secretary of State Hillary Clinton - who has been particularly conspicuous for her silence about the region's repression - has suddenly begun speaking up about the need for change.

In a speech Thursday at the Forum for the Future conference in Doha, Qatar, Clinton talked about the frustrations of the under-30 generation in finding work and bluntly added that "people have grown tired of corrupt institutions and a stagnant political order." She then called for "political reforms that will create the space young people are demanding, to participate in public affairs and have a meaningful role in the decisions that shape their lives."

It may be too late for the United States to head off a rolling social upheaval in the Middle East this year - or a war involving Hezbollah and Hamas. But if it follows up on what Clinton has been saying, it can at least place itself on the right side of those events.