Could 2012 turn conventional wisdom on its head? Here’s the conventional wisdom: President Obama’s reelection is vulnerable to the weak economy and high joblessness. Here’s what might happen: The economy gradually improves, and although unemployment stays high (exceeding 8 percent), what counts politically is the palpable sense that things are moving in the right direction. This allows Obama to argue, as he already does, that his policies are slowly repairing the economic calamity he inherited from Republicans.

To which they respond: Obama’s anti-business rhetoric and policies have impeded recovery; the Affordable Care Act (“Obamacare”) and new regulations create uncertainties that deter hiring; and Obama hasn’t dealt with the explosion of federal debt.

Just which narrative triumphs may well determine the election. If Obama convinces Americans that he’s set a course for a stronger recovery, then he wins. If the Republicans successfully cast his policies as producing prolonged stagnation, they win. Though the debate matters, the economy’s actual performance — for better or worse — will decide how many Americans feel. And this will depend on forces and events over which the candidates have little or no control.

What’s the 2012 outlook?

Many forecasts see modest growth. Here are some numbers from IHS Global Insight, a major consulting firm. The economy will expand 1.8 percent, almost the same as in 2011 (estimate: 1.7 percent). Payroll jobs will grow about 145,000 a month, rising gradually; that’s decent but probably wouldn’t cut the unemployment rate. Indeed, normal labor force growth and the prospect that some discouraged workers will start looking for jobs indicate the unemployment rate (8.6 percent in November) could average 8.7 percent, only slightly below the 9 percent of 2011.

This forecast depicts a plodding economy; should it materialize, it would favor the Republicans. “Consumers face too many negatives to allow a robust spending recovery — a weak labor market, high debt burdens, house prices that have not yet hit bottom, price increases that have outpaced wage growth, and a lack of confidence in the government’s ability to make things better,” says IHS.

But the mainstream forecast may be too glum. Starting with the 2008 financial crisis, economic predictions have routinely been wrong. At this time last year, they were too optimistic; now they might be too pessimistic. Many indicators are exceeding expectations. Weekly initial claims for unemployment insurance, which peaked at more than 600,000, are running under 400,000 — a level often associated with a low or declining unemployment rate. Housing construction was up 9.3 percent in November over October and 24.3 percent over November 2010.

For Obama, the economy holds two large potential pluses.

First, there’s huge pent-up demand for homes and vehicles, because both sectors collapsed in the recession. Car and light-truck sales, which totaled about 17 million annually in 2004 and 2005, fell to 10.4 million in 2009. In 2011, IHS estimated sales to reach 12.7 million. The decline in housing construction was even deeper, from about 2 million units annually in 2004 and 2005 to an estimated 600,000 in 2011.

Second, the consumer debt burden is dropping rapidly, notes Timothy Taylor, managing editor of the Journal of Economic Perspectives, on his blog. Households have repaid some debts. Others have been written off; interest rates on many remaining loans have declined. On average, households paid 16.15 percent of their income toward loans, rents and leases in the third quarter of 2011, according to Federal Reserve data. That was the lowest since 1993 and down from a peak of 18.85 percent in the third quarter of 2007.

The upshot: More Americans may be in a position to borrow to buy a home or vehicle, relieving some pent-up demand. Home sales may already be reviving. In November, new contracts reached their highest level in 19 months.

By contrast, Europe and China pose big risks. In Europe, Italy and Spain have nearly 500 billion euros worth of maturing debt in 2012, reports the Institute of International Finance. If they can’t refinance — if bond markets won’t renew loans at acceptable interest rates — they would default or need to be rescued. Either way, Europe would face greater austerity and a deep recession. This would hurt U.S. exports and the profits of American multinational firms.

The danger from China is a collapsing real estate “bubble” that, if it occurred, would result in bankruptcies of developers, loan losses to banks and slower economic growth. The effects would spread beyond China, because construction fuels its demand for cement, steel, copper and other raw materials traded on world markets. Again, U.S. exports could suffer.

Given all the possibilities, handicapping the election based on the economy is nearly futile. It’s 2012’s political wild card that — when played — may prove decisive, if accidental.