This month marked 15 years since the signing of the Israel-PLO Declaration of Principles on the South Lawn of the White House, launching the Oslo process and a new hope for the Middle East. The anniversary was largely ignored, overshadowed by the latest rounds of political uncertainty and upheaval in both Israel (where the ruling Kadima party elected Tzipi Livni its new leader) and in the Palestinian territories. Indeed there was little cause for fanfare or celebration. The latest incarnation of Oslo, the Annapolis effort, is sputtering toward another unrealized peace deadline, the end of '08.

For some this latest Annapolis failure is another "almost moment" in a fundamentally sound process that has been bedeviled by near misses of timing, politics, personalities and just plain bad luck. Others roll their eyes - there can never be peace in the Holy Land, the two-state solution is a dream, better to move on to something more promising. A few contrarian souls tout alternative plans to the two-state solution - some even appear beautiful in power-point presentations - none seem to have any chance of gaining acceptance, let alone majority support among both publics.

The two-state solution remains the only option that has real popular traction with both Israelis and Palestinians. It may very well still be attainable, but 15 years later it is probably fair to say that the Oslo model will not be the formula for getting there.

The peace process framework bequeathed by Oslo endures to this day, but it suffers from severe structural flaws. First is the idea that the parties, as part of a gradual process, can build confidence on issues like settlements or security without actually defining the endgame. The future is unknown and the present is adversarial, unsurprisingly the product is not a relationship of trust.

Second is the notion that institutions of statehood can be built, a fledgling Palestinian economy can thrive and that a Palestinian Authority can balance domestic credibility with being an Israeli security sub-contractor, all under conditions of ongoing, hostile foreign occupation. It does not work.

Third, Oslo began life as a bilateral Israeli-Palestinian negotiating process (the Norwegians were wonderful and effective hosts, not deal-brokers). When it comes though to reaching closure on the toughest issues - exact borders, how to dividing Jerusalem, finessing language on refugees, it is unlikely that the parties, with the political baggage that they carry, can do this alone. Nobody, though, has actively carried the parties over the finishing line.

Finally, Oslo and its progeny of peace efforts have been too much about getting an Israeli-Palestinian deal in isolation from broader regional developments in the Middle East. The Syria track has its impact, how Iran is managed is a shaping factor, as is the disposition of the Gulf and other Sunni-Arab states. There has not been a comprehensive regional effort led by the United States or the international community.

To all this one should add that the existing Oslo framework was ill-equipped to deal with the emergence of democratic, multi-party politics in Palestine. The political success of Hamas does not have to mean the end of the two-state solution, but the way the Hamas issue has been managed could produce that outcome.

The Bush administration's Annapolis effort indulged too many of these structurally embedded obstacles. The temptation for the next U.S. government will be to try a 16th and then subsequent years of the same approach. A new administration may bring greater enthusiasm and energy and may even appoint an envoy, but the results will likely be as familiar as they are unflattering, absent a major structural adjustment. In its mid-teens the Oslo process suffers from the law of diminishing returns - at each unsuccessful turn confidence is sapped, pragmatism tarnished, and skepticism entrenched.

The two-state solution does retain a resilience and considerable popular support, if only for lack of attractive, realistic alternatives. Yet even this resilience cannot withstand further failures and setbacks - potentially leaving Israel, its American ally, the Palestinians and the region with no workable medium-term solutions.

After 15 years certain conclusions are both overdue and urgent; final borders are needed (sustainable CBM's and Palestinian institution-building don't work under occupation); solutions will require a region-wide and inclusive approach (especially with Syria and Hamas); actual de-occupation will have to be front-loaded while providing Israel with international and regional security guarantees, manifested in a physical troop presence; and all this should be externally driven, and U.S.-led. Internalizing this reality and acting on it is probably the only way to still implement the vanishing Oslo vision of two states.