The general election is shaping up as a contest between two remarkably similar men. Not ideologically. Despite the Newt Gingrich-peddled notion that "there really is no difference" between Mitt Romney and Barack Obama, the gulf in political philosophy is enormous.

Both men, left to their own devices, would occupy a centrist place within their own parties. But Obama envisions a far more muscular role for government in general and the federal government in particular. Romney's faith is primarily -- excessively, in my view -- in the free market.

Still, assuming that Romney becomes the Republican nominee, the two candidates will share surprisingly similar temperaments and habits of mind. They are different from the standard-issue politician -- both are more aloof than gregarious, more cerebral than impassioned.

These similarities could not have been predicted from their entirely different backgrounds. Romney came from wealth; Obama's mother was for a time on food stamps. Romney idolized his father; Obama scarcely knew his. Romney's upbringing was defined by his Mormonism; organized religion was not part of Obama's early life.

Romney's was a white, suburban childhood out of "Father Knows Best." Obama's was multiracial and helter-skelter -- in Hawaii and Indonesia, living with his mother or left with his grandparents.

Yet somehow from these different environments emerged two men shaped by a sense of outsiderness.

"From early childhood, he formed his views through observation and analysis, by hanging back as the world unfolded before him," Michael Kranish and Scott Helman write in "The Real Romney."

David Maraniss, whose Obama biography, "The Story," will be published in June, describes the president in similar terms. Much like his mother, "Obama is an anthropologist -- a participant/observer," Maraniss told me.

Both men lack the typical politician's craving for external approval and validation. They exhibit a disdain for the ordinary obligations of political life, whether endlessly posing for photos (Obama) or robotically delivering a stump speech (Romney).

Obama and Romney are less back-slappers than report-readers, technocratic elitists with an abiding faith in the meritocracy. Confronted with a problem, their instincts are to assemble the experts and split the difference. It is no accident, then, that their health care programs share the distinguishing -- perhaps politically disqualifying -- feature of requiring individuals to obtain coverage.

Finally, both men reflect a certain ideological inscrutability, despite years in the public eye.

"To this day, he remains an enigmatic presence to people outside his closest circle, a puzzle whose pieces don't neatly fit," Kranish and Helman write of Romney. For Obama, that essential mysteriousness -- Is he a liberal? A moderate? -- has been more of a plus, inspiring voters to pour their hopes into an undefined vessel. He is a self-proclaimed Rorschach test for voters to interpret at will.

The Obama-Romney comparison is admittedly imperfect. Obama's is a graceful aloofness; he comes off as cool but not needy. Romney is awkward in his aloofness; he tries too hard to connect. The difference between the two candidates is the difference between crooning Al Green and reciting obscure verses of "America the Beautiful."

Yet the similarities are striking. As the campaign grinds into the general election phase, these traits will, I predict, become all the more evident and intriguing.