The last time I considered Barack Obama’s re-election chances in this magazine, in mid-November, things were looking pretty bleak for the president. The statistical model I used measured three key factors — a president’s approval rating, economic growth and the ideological orientation of his opponent — and taken together, they showed that Obama had become a slight underdog to win re-election.

Three months later, his position is much stronger.

In January, 243,000 jobs were created. The number surprised investors and economists, but it was part of a stream of solid economic data: over the last few months, consumer confidence has gone up, Americans have spent more on big-ticket items like cars and there is even evidence that the housing market has begun to rebound. Before the job numbers came out, most economists were expecting around 2.5 percent G.D.P. growth this year. Those forecasts are liable to be revised upward now, perhaps to about 3 percent.

Americans seem to have noticed the change. By early February, Obama’s approval rating had climbed to 49 percent in the Real Clear Politics average, a six-point improvement from three months earlier. Although it’s not a terrific approval rating, it may be enough to get Obama another term. In 2004, George W. Bush won a narrow victory with essentially identical metrics: G.D.P. growth of 2.9 percent and an approval rating of about 48 percent on Election Day.

Still, Obama’s position isn’t solid enough for him to beat just anybody. Bush benefited from running against a middling opponent like John Kerry, against whom he was able to squeeze every ounce out of his approval rating.

The model I created evaluates the strength of the opposition candidate by considering his ideology on a left-to-right scale. Candidates who are closer to the center have historically done better than those closer to the wings. (I’ve updated the model’s measure of ideology to account for new data.)

Obama’s most likely Republican opponent, Mitt Romney, continues to rate as a “generic Republican.” In fact, he now scores at exactly 50 on the 100-point scale from centrist to extremist. That means an election against Romney, like Bush’s against Kerry, would mostly be dictated by the fundamentals of the economy and by evaluations of Obama’s job performance. With 2.5 percent G.D.P. growth from now through November, Obama would be a 60 percent favorite to win the popular vote.

The popular vote is one thing, however. The Electoral College is another — and Romney could have more vulnerabilities there.

In recent weeks, Obama has taken a more populist approach (just read the transcript of his State of the Union address). The strategy has induced more howls than usual from Republicans about “class warfare,” but the White House has clearly studied the numbers. In the Republican primaries, Romney has had trouble winning the loyalty of working-class voters, especially in the Midwest. And recent polls suggest that Romney, who has a penchant for making intemperate comments that draw attention to his wealth, could struggle among that group in the general election as well.

So let’s conduct a thought experiment. Suppose that against Romney, Obama does 10 points better among white voters whose households make less than $50,000 per year. The trade-off is that he does 10 points worse among whites making $100,000 or more and 15 points worse among whites making at least $200,000.

In terms of the popular vote, this would almost exactly balance out. The effect would be more substantial, however, in individual states.

In wealthy Virginia, Obama would lose a net of 2.5 percentage points to Romney under these rules, according to the demographics from the 2008 exit poll there. He would also be harmed by 2.7 points in Colorado. And Romney would have a chance of putting New Jersey into play, because he would gain four full points there. (The Chris-Christie-for-V.P. train will be departing from Platform 1.)

Moreover, Obama would have relatively few states that he might flip to blue. Missouri is one exception: the 3.9-point boost he would see there outweighs his narrow margin of defeat in 2008. Obama would also gain 5.8 points in Montana, which would have been enough for him to beat John McCain.

But Obama doesn’t need to win many new states. His challenge will be in holding the ones that might turn red. And pursuing a populist strategy against Romney could put him at a big advantage.

Consider the Midwest. By trading votes among wealthy whites for more among working-class ones, Obama would bolster his margins in Ohio, Wisconsin, Iowa and Michigan. Indiana, a state that otherwise looks like a very tough hold for Obama, also contains a high percentage of working-class whites, and he could gain a few points there.

His chances of winning North Carolina, where he sneaked by with fewer than 15,000 votes last time, would go up as well. The same goes for the 2nd congressional district in Nebraska, and Oregon and Maine, two states that are less upscale than their coastal brethren and that have been competitive in the past, would be easier holds.

Conversely, none of the 22 states that John McCain carried in 2008 would be bolstered meaningfully under this situation. Most of those states are securely Republican to begin with; the few exceptions, like Georgia and Arizona, contain about as many working-class whites as wealthy ones.

All told, there are 101 electoral votes in swing states that Obama could either put into play or make more secure under the populist paradigm — well more than the 36 he might lose among Virginia, Colorado and New Jersey.

The reason for the imbalance is that most wealthy whites do not live in swing states but in enclaves that the sociologist Charles Murray calls SuperZIPs. Most of these are in states like New York, California, Maryland and Massachusetts that are very far from being competitive. (There are also a significant number of SuperZIPs in the Dallas and Houston metro areas in Texas, but Obama probably wasn’t going to win the Lone Star State anyway.)

But what if Rick Santorum were to steal the Republican nomination away from Romney? After his sweep of the contests in Colorado, Minnesota and Missouri on Feb. 7, he looks like a more viable candidate — one who doesn’t seem as beholden to the 1 percent as Romney does. He has been successful at making Obama’s supposed elitism a theme of his campaign. And he is more conservative on social policy than on fiscal policy, which runs against the consensus view in the Virginia and New Jersey suburbs but puts him in line with the preferences of middle-income voters in the center of the country.

Still, Santorum, who rates as a 68 on the ideology scale (the same as a less-plausible nominee, Newt Gingrich), would probably be weaker than Romney in the popular vote. According to the model, Obama would be a 77 percent favorite to win the popular vote against Santorum given 2.5 percent G.D.P. growth.

Republicans wouldn’t care about that, however, if Santorum carried Ohio and Michigan — and perhaps even his home state, Pennsylvania — places where economic concerns tend to take precedence. Under these conditions, in fact, Republicans might be able to win the Electoral College while losing the popular vote.

I am not quite ready to suggest that Santorum would be a better nominee than Romney. But the electability gap between the two is closer than it might appear because of the way Santorum’s strengths could play in the Electoral College. At the very least, he might force a reset of the White House’s strategy — from one focused on the 99 percent to one more intent on critiquing Santorum’s positions on social issues.

Whichever strategy the Obama folks settle on, though, they’ll be acting from a place of relative strength — so long as the economic numbers remain decent. If the economy tips backward toward recession because of the situation in Europe or tensions in the Middle East, Obama would go right back to being an underdog against either Romney or Santorum.

So, who wants to bet on there being nine months of no bad news?