The Romney camp is feeling cautiously optimistic. Public polling confirms the campaign's internal polling and sense of the election: It is a “margin of error race.” That has unintentionally two meanings.

The first is that the race is determined by small vicissitudes in the race that pull undecided voters one way or another. Bain Capital attacks nudge them away from Mitt Romney. “You didn’t build that” sends them careening away from President Obama. The goal here is to be the last man standing with more money than the other guy to go up with ads in the final days of the race. Call this the Pundit Theory of the race. (In fairness it is also the Consultant Theory of the race since consultants make a mint on cranking out ads and moving, they say, the electorate around the game board.) Under the Pundit Theory you don’t want to make errors, because errors, gaffes and missed opportunities can determine the outcome.

The other theory of the race I’ll call the Big Picture Theory. In this framework, basic economic facts (unemployment, recession, GDP) and voters’ reactions to those (right track/wrong track, who handles the economy better) define the race. (Numerous models are created to predict the election outcome purely on economic data.) There are those who would look at Obama’s under-50 percent approval, the lagging economy and the wrong track figure (over 60 percent) and say there isn’t much the candidates will do short of a scandal or horrendous flub that will change the trajectory of the race (in favor of Romney). Moreover, voter enthusiasm, which now leans Republican, will be key. The “error” here refers to the actual “margin of error” in the polls, suggesting the race is very, very close because we have a very, very polarized electorate.

Aside from giving them something to write about, pundits like the Pundit Theory because it makes their “analysis” very important. It puts great stock in minute changes in polls and in the daily headlines. It is also the sort of race the Obama team wants, one in which negative ads, tangential issues, and pumping up this or that interest group can win the race. If you focus on the economy and the economic outlook for he next few months, it’s far more depressing for the Obama team than imagining one more error by the other side or one more ad by your side will do the trick.

It’s not surprising that the Romney team is generally attuned to the Big Picture Theory. It is more comforting to think that the die has been cast by the limp Obama economy. But even the Romney team would readily concede that “at the margins” execution does matter. Rep. Paul Ryan (R-Wis.) started strong, and if he keeps it up he may add a point or two in Wisconsin or in the suburban neighborhoods of key swing states. Coming out on offense on Medicare, they think, was critical. The Romney campaign understands that in a really close race changing voters’ perceptions “at the margins” can be the difference between victory and defeat.

But the Romney’s main concern, at least it should be, is in showing Romney and Ryan to be nonscary, competent people with ideas about how to fix the economy. They do that, the reasoning goes, and the economy plus Obama’s lack of substantive policies to change the course of the economy can get them to 270 electoral votes.

Which side is right? On balance I think the “story of the day” is really just noise and the fundamentals in the race haven’t changed since Romney got the nomination. But that belief should not lead the Romney campaign (as we have sometimes seen) to be passive, overly cautious and run purely on a not-Obama message. In fact, part of winning on the economy has to do with showing voters that Obama’s ideas for fixing the economy are wrong (or nonexistent) and Romney’s are reasonable. Getting that essential message across and then turning out supporters will, I believe, determine who wins.