WASHINGTON - John Kerry's high-stakes gamble that he could finally achieve the dream of generations and bring peace to the Middle East seems to be collapsing as easily as a house of cards.
Despite a dozen visits to Israel and the West Bank since he became US secretary of state 14 months ago and many more late-night meetings with his recalcitrant partners in capitals around the world, it appears after all that he may have been trumped.
While there was always a certain hubris to his mission impossible, the political dangers facing wily Israeli Prime Minister Benjamin Netanyahu conspired this week with decades of pent-up anger among Palestinians to throw up the most serious crisis to the fragile peace negotiations since they resumed in July.
Yet at the start of Kerry's latest overseas trip there was little to suggest he would return to the US 13 days later with his peace effort in trouble and a blunt admission that he and the White House needed to "evaluate" the next steps.
Indeed, Kerry had not visited Israel in three months in a tacit recognition that each trip raised expectations and usually triggered some kind of provocative move from one of the parties.
His monthly commute between Washington and Jerusalem had also begun to raise eyebrows with little tangible progress to show and an April 29 deadline looming.
Israeli Defence Minister Moshe Yaalon had called Kerry "obsessional" and "messianic" and at home some critics said he was "delusional."
All roads to Jerusalem are littered with past failed peace negotiations which have wound through places such as Madrid, Oslo and Camp David.
But this time Kerry felt there was something within his grasp, a deal under which both sides would agree to keep talking into next year, as some of the nitty-gritty contours of a pact began to emerge.
He deeply believes that a comprehensive peace treaty is the only way to secure Israel's future and build a better tomorrow for Palestinians, with both peoples having suffered too much.
So the 70-year-old former senator, the son of a diplomat, stepped willingly into the quagmire that is Middle East peace.
He has invested huge amounts of energy, setting a punishing schedule which would defeat many half his age and remaining eternally optimistic and unflappable even after hours locked in tense negotiations.
It was sobering therefore on Friday as he prepared to head home - after the Israelis cancelled the last prisoner releases and the Palestinians said they would seek statehood at 15 agencies at the UN - that in a rare moment of frankness and frustration he admitted "it's reality-check time." "There are limits to the amount of time and effort that the United States can spend if the parties themselves are unwilling to take constructive steps in order to be able to move forward," Kerry told reporters in Rabat.
With the war in Syria, Iran's nuclear programme and the crisis in Ukraine, "we have an enormous amount on the plate," he said.