This tendency helps to explain the huge advantage enjoyed by most incumbents: if a sitting president looks even vaguely competent and reliable, threatening few unpleasant surprises or boat-rocking agendas, he most always wins reelection. When there’s no White House occupant on the ballot (as in 2000 or 2008) the public will generally choose the candidate who acts most like an incumbent—George W. Bush in 2000 and Barack Obama in 2008. By contrast to their measured, cool-customer demeanor, their opponents looked erratic and unpredictable: Al Gore seemed weird, unstable, gaffe-prone, and condescending; while John McCain was hyper-caffeinated, jumpy, and increasingly desperate in coming to terms with the financial meltdown.

Mitt Romney is running like an incumbent candidate, and it seems to work for him. By a wide margin, he came across as the least scary, least risky, most cautious choice on the stage at Myrtle Beach.

This may not produce huge enthusiasm in the Twitterverse (Fox News is already reporting that Ron’s Paulestinians gave him, as always, the most energetic response in social media), but it’s given Romney a huge lead in national opinion polls.