Usually, Immelman will uncover journalistic evidence for (or against) about 40 of these 170 traits, which he then groups into broader patterns, like extroversion, that are weighted to reflect the results of past elections. (Clinton won twice as an extrovert, for example, so extroversion is worth a lot of points.) When combined, these categorical tallies produce a single score: the Personal Electability Index (PEI). High scores don’t always correlate with victory; Michele Bachmann has what Immelman describes as “a very favorable score,” even though she’s a long shot for the Republican nomination. But candidates with low PEI scores almost never get elected.

Romney’s score is a six, which is abysmal. Barack Obama, by comparison, earned a 28, and even failed candidates such as Hillary Clinton and John McCain have cleared 20 (23 and 26, respectively). Romney’s problem, according to Immelman, is that modern voters tend to reject two personality types in particular: introverted people, who would “rather lead a life of their own mind than relate to others,” and conscientious people, who are “proper, diligent, detail-oriented, and super-rational.” Romney isn’t especially introverted, but his conscientiousness is pronounced; in fact, it is the only trait of his that qualifies as clinically “prominent.”

In the past, Romney’s personality may not have hindered his campaign. A number of presidents, including Herbert Hoover, Calvin Coolidge, Woodrow Wilson, and even James Madison won the White House because (not in spite) of their most Romneyesque qualities: politeness, caution, restraint, systematic thinking, a sense of duty, and so on. But while earlier eras rewarded calculation—until the mid–20th century, public persuasion mattered less than methodical behind-the-scenes maneuvering—the 24/7 news cycle forces candidates to connect. “The opposite of conscientiousness is impulsiveness, so you’d think voters would like conscientious politicians,” says Immelman. “But they don’t, at least not anymore. On TV, a conscientious person will come across as stiff, because they are not emotional—they’re rational.” Much like Bob Dole, Bill Bradley, Michael Dukakis, and Al Gore—the other “conscientious” candidates of the television age, according to Immelman—Romney is calculating when he should be connecting…

The only mystery now, the only surprise left, is Romney vs. Obama. Supporters say that Romney would be “more himself” in a general-election setting, where he’d no longer have to pander to the Republican fringe. But it’s possible, too, that being himself would be the problem. In America, voters tend to replace sitting presidents with polar-opposite personalities: Jimmy Carter and Ronald Reagan, George H.W. Bush and Bill Clinton, George W. Bush and Obama. But as Aubrey Immelman points out, the rational, technocratic Obama “is one of the few presidential candidates since 1996 who can be labeled conscientious,” just like Romney. Faced with a choice between the conscientious devil they know and the conscientious devil they don’t, voters may not be as motivated to switch sides—especially when the incumbent scores higher on empathy, confidence, and comfort in his own skin.