First, recent polls showing him losing were on the verge of becoming self-fulfilling prophesies by discouraging his supporters and inspiriting Obama’s. Romney, unleashing his inner wonk about economic matters, probably stabilized public opinion and prevented a rush to judgment as early voting accelerates.

Second, Romney needed to be seen tutoring Obama on such elementary distinctions as that between reducing tax rates (while simultaneously reducing, by means-testing, the value of deductions) and reducing revenues, revenues being a function of economic growth, which the rate reductions could stimulate.

Third, Romney needed to rivet the attention of the electorate, in which self-identified conservatives outnumber self-identified liberals 2 to 1, on this choice…