For almost 14 years, the United States’ military prison camp in Guantánamo Bay, Cuba, has sat festering on the edge of the Caribbean and the Constitution. Opened by President George W. Bush in the panicky months after the Sept. 11 attacks, the detention center has had a powerful radicalizing effect, has severely tarnished America’s standing as a nation of laws and has cost taxpayers more than $5.2 billion.

This travesty could and should have ended years ago. But Congress has gone to great lengths to keep the prison open. Within the executive branch, agencies have sometimes worked at cross-purposes and at times dragged their feet. In the end, however, the buck stops with the president.

President Obama made closing Guantánamo a central promise of his first campaign for the White House. But it remains unfulfilled because of his team’s political misjudgments, dogged opposition in Congress and his failure to use his authority more aggressively. Mr. Obama has just over a year left to fulfill his pledge. The goal remains daunting, but it is not impossible.

The White House and the Pentagon will soon present to Congress a detailed plan for closing the prison. It will involve a ramping up of releases of those who have been cleared to leave and the transfer of the rest to prisons or military facilities in the United States. This proposal represents the best chance of breaking the political and bureaucratic logjams that have kept Guantánamo open.