Note: The following article was written by Nigel Gault and Erik Johnson. Gault (right)  is Chief US Economist for IHS Global Insight and will speak at the November 18 AIM Executive Forum in Waltham.

Based on the expected state of the economy, President Obama faces an uphill battle to win reelection in 2012. He will need a combination of an economic rebound over the next 12 months and an ineffective Republican candidate if he is to retain the White House.

Over the years, statistical attempts to explain and predict U.S. presidential election results have yielded two overarching themes.

First, Americans tend to vote their pocketbooks. If the economy is growing strongly and unemployment is low, the incumbent party has a very good chance of retaining office. When the economy is faltering, U.S. voters will more likely vote for change.

Second, Americans tend to favor an incumbent president running for reelection. If the economy is weak enough, however, an incumbent president can lose, as Jimmy Carter learned in 1980 and George H. W. Bush did in 1992.

Based on the likely state of the economy in 2012, President Obama faces a steep uphill task to secure reelection.

Based upon our forecast for the economy, our election equation projects just a 43.5 percent share of the two-party vote for the president, i.e., a heavy defeat. This does not mean that the president’s re-election campaign is doomed, though. The economy might perform better than we expect, and if voters perceive the economy to be on the mend, the president still could win even if unemployment is still very high (as seems inevitable).

Just as important, if not more so, the election equation takes no account of the identity of the candidates—a Republican opponent lacking broad appeal could tilt the balance back in favor of the president. But it does appear that this is an election that is the Republicans’ to lose.

How Could President Obama Win Reelection?

Despite the results of our election equation, the Republicans are not guaranteed the White House in 2012.

It may be that voters will respond to economic factors in a different way than in the past. Having seen the unemployment rate climb as high as 10.1 percent a year into Obama’s presidency, voters may be more tolerant of an unemployment rate around 9.0 percent as the election nears.

Some voters may discount Obama’s accountability for the current state of the economy and still assign much of the blame to his predecessor, George W. Bush. If the president can deliver faster income growth over the next year, voters may assign more weight to income growth and less weight to the unemployment rate than in past elections, opening the door for the president to win a second term.

In addition, non-economic factors also matter. The equation assumes that the only factors influencing the election result (other than objective, predetermined political factors) are income growth and unemployment. It ignores factors such as foreign policy and social agendas, as well as any qualifying data about the candidates on either side. The topic of electability has become increasingly relevant in recent years, and the equation is built to predict election results based on the average Republican or average Democrat, making no special considerations for African-American, female, or politically extreme candidates (or for their vice-presidential nominees).

The Republicans do not yet have a candidate who commands anything close to majority support in their party. Front-runner Mitt Romney has not decisively separated himself from the rest of the field, suggesting that Republicans are seeking an alternative but have not found it. And their candidate must win broader appeal in the general election. The traditional unwritten rules say that candidates swing to the right or left in the primaries to capture their party base, and then swing to the center in the general election to capture independents and disaffected members of the other party. President Obama must hope that the Republican candidate, whoever that may be, cannot make that transition.

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