But interviews with people from the candidates’ overlapping realms — at Harvard, in the health care policy arena and in politics — yield similar observations about their personalities and their leadership and decision-making styles. Both are analytical introverts operating in a province of extroverts…

Neither candidate has much stomach for small talk or idle chatter. They have both been called difficult to know and even aloof at times. But if they were to convene for, say, a chicken barbecue — not likely, but whatever — they could explore some shared affinities and experiences. After-dinner, for instance, maybe over plates of pie (enjoyed by both), Mr. Obama and Mr. Romney could play the “did you know” game from their Harvard days or name-check the policy experts they consulted during their respective health care overhauls…

Mr. Romney “struck me as someone who was more interested in having the job as governor than doing the job,” said Gov. Deval Patrick of Massachusetts, a Democrat and close friend of Mr. Obama who succeeded Mr. Romney. Mr. Patrick said his predecessor, whom he describes as “a gentleman,” seemed to be someone who said to himself, “O.K., I won that, now I’m going to move onto something else.” Former Senate colleagues of Mr. Obama said the same about the future president.

There is a restless quality to both Mr. Obama and Mr. Romney, people close to them say. They spent formative periods living abroad and attended several colleges before carving out political careers as above-it-all outsiders. They had their convictions questioned by ideological purists in their parties (and their religions, too, by others).