In his opening to China more than 40 years ago, Richard M. Nixon made a huge Cold War gamble that he could forge a working relationship with a Communist country that had built a small arsenal ofnuclear weapons and clearly had long-term ambitions for global power.

For President Obama, the deal struck Tuesday morning with Iran represents a similar leap of faith, a bet that by defusing the country’s nuclear threat — even if just for a decade or so — he and his successors would have the time and space to restructure one of the United States’ deepest adversarial relationships.

Mr. Obama will be long out of office before any reasonable assessment can be made as to whether that roll of the dice paid off. The best guess today, even among the most passionate supporters of the president’s Iran project, is that the judgment will be mixed.

Little in the deal announced on Tuesday eliminates Iran’s ability to become a threshold nuclear power eventually — it just delays the day. To Mr. Obama’s many critics, including Henry A. Kissinger, the architect of the China opening, that is a fatal flaw. It does nothing, Mr. Kissinger wrote recently with another former secretary of state, George P. Shultz, to change “three and a half decades of militant hostility to the West.”

Read the article “Iran Nuclear Deal is a Huge, Historic Gamble” on nytimes.com.