Kerry is just days away from his 70th birthday. His wife has health problems. He could be sailing, or playing hockey, or writing his memoirs from the vantage point of a peaceful retirement. But his enthusiasm for his current job is unquestionable; one aide told me that he will have to be dragged from the office—fingernails scraping against the floor—at the end of his term.

“I’m very blessed to be in a position where I can work on these issues full-time without having to go out and raise money and without having to worry about, you know, the sort of domestic politics of it,” he told me this fall. “I can just focus on the substance, focus on the challenge, focus on the facts, and try to get something done. And I like that. I find it very rewarding and a lot of fun.”

One can understand how being freed from constant fund-raising and politicking would be liberating. Beyond that, though, his aides say that becoming secretary of state has allowed him to be himself in a way that being an electoral politician didn’t. As a presidential candidate, he had to downplay his obsession with foreign policy and his fluency in foreign languages, for fear that such things would play badly with voters; as secretary of state, he can freely leverage those qualities.

Of course, if there is no breakthrough with Iran, or if his efforts to broker peace in Syria fall short, or if the Israeli-Palestinian peace talks founder, history will likely view Kerry as the tragicomic figure his detractors already judge him to be. But while traveling with Kerry around the Middle East over several months last spring and early summer, I came to believe that he might succeed in proving the skeptics wrong. “He will just never give up,” Lowenstein told me.

In many ways, secretary of state is the job for which Kerry was born and bred.

Born: His father was a Foreign Service officer who spent years as a diplomat in Germany and Norway; his mother was the Paris-born scion of Boston’s Forbes family, at whose estate in Brittany, France, Kerry spent his summers as a boy. In the summer of 1962, after Kerry graduated from prep school, he dated Janet Auchincloss and visited her at her family’s palatial estate in Rhode Island, which the Kennedy administration was using as a summer White House. Kerry met Kennedy there, and that September he watched the America’s Cup sailing race with the president and his friends.

Bred: While volunteering for service in Vietnam as a naval officer, he was awarded a Bronze Star, a Silver Star, and three Purple Hearts. Upon his return home, Kerry became an antiwar activist and, on April 22, 1971, the first Vietnam veteran to testify before Congress. Following stints as an assistant district attorney and the lieutenant governor of Massachusetts, Kerry would, after his election to the Senate in 1984, go on to serve for 28 years on the same committee he had stood before in 1971, the Senate Foreign Relations Committee. Logging thousands of miles on fact-finding expeditions—a trip to Nicaragua in 1985 to meet with President Daniel Ortega; serving as a crucial envoy to Pakistan and Afghanistan in 2011—he developed diplomatic contacts worldwide. He also, of course, lost the 2004 presidential election to George

W. Bush, after a campaign premised on the idea that he would manage America’s foreign policy more prudently. (But for Ohio, where he lost to Bush by 119,000 votes, Kerry would have been president.)