Finally, President Biden got his Rose Garden peace deal. It was not exactly the one he has been straining to land for most of the past year, but it was a breakthrough nonetheless — and, coming after a bitter election, a sweet moment of validation.

The question is whether the cease-fire in Lebanon that Mr. Biden announced on Tuesday will be the coda to his diplomatic efforts in the Middle East or a steppingstone to more sweeping agreements that could at last end the devastating war in Gaza and potentially even set the stage for a broader regional transformation.

If it holds, the Lebanon cease-fire by itself could make an important difference. It was designed to restore stability along the border between Israel and Lebanon, permitting hundreds of thousands of displaced civilians on both sides to return to their homes while providing a buffer zone to ensure Israeli security and offering an opportunity for Lebanon’s government to reassert control over its territory from a weakened Hezbollah.

But as he stepped out of the Oval Office into the Rose Garden on a sunny November day in the winter of his presidency to hail the agreement on Tuesday, Mr. Biden clearly had grander ambitions still in mind. “It reminds us that peace is possible,” he said. “I say that again: Peace is possible. As long as that is the case, I’ll not for a single moment stop working to achieve it.”

With just 55 days left in office, Mr. Biden is racing against the clock of history. He would prefer to be remembered as the president who set the Middle East on a path toward a lasting settlement of longstanding animosities than one who turned over a mess to his successor.

With the Lebanon accord in hand, Mr. Biden said he would now renew his push for a cease-fire in Gaza, working along with Egypt, Qatar and Turkey, and he called on both Israel and Hamas to seize the moment. He described the cataclysmic violence that Palestinians have endured in Gaza in more visceral terms than he typically has over the past 14 months of war.