With America so evenly split politically, compromise would seem to beckon. For policy, it offers possible solution to long festering problems. For politics, it offers the prospect of seizing the center on which victory appears to balance. 

However it is neither policy nor politics that reveals why “center politics” does not prevail… it is economics. Near-balance makes compromise less likely, not more so, because this when its risk/reward ratio — i.e., its political cost — is highest. 

America’s close and deep divide is plain. Barack Obama won the popular vote in 2008, 52.5 percent to 46.2 percent. According to November 2010 midterm election exit polling, Obama’s approval/disapproval rating was 44 percent/55 percent. According to a 3/5 Gallup tracking poll, Obama’s approval/disapproval ratings are 45 percent/48 percent. And according to the latest NBC/Wall Street Journal poll, he leads Mitt Romney, his closest challenger, 50 percent to 44 percent.

Average these numbers from the last four years and you come up with a 47.9 percent to 48.3 percent difference. That’s extraordinarily close. 

Such even balance implies the electorate’s center is determinant. So the incentive would seem to be to boldly strike toward it: Offer compromise and play for election-deciding Independent voters. 

The reason a “play to the center” strategy does not prevail is that a candidate can win with a vote percentage well below 50 percent. Clinton twice won the presidency with sub-50 percent levels — 42.9 percent in 1992 and 49.2 percent in 1996. As 2000 showed when Bush beat Gore, even having more popular votes does not guarantee victory. 

Sub-majority victories often come when one party splits its base — providing the other party a golden opportunity. Nader did it in 2000, costing Gore Florida and the election; Perot did it in 1992, costing Bush I what should have been a convincing victory; and famously, Teddy Roosevelt did it in 1912, making the incumbent Taft finish third. 

These elections demonstrate the risk inherent in “playing to the center.” With the two sides as evenly balanced as they are now, the voters up for grabs in the center represent a small fraction of the total voters. To make a concerted play for them, a party simultaneously risks its base supporters.

As the two sides both near a majority, the ratio of potential supporters to secure supporters decreases. The “reward” therefore decreases too. Conversely, the risk increases as the proportion of secure supporters to potential supporters increases.

The opposite dynamic also occurs. A party is most motivated to “play to the center” when it is further from the majority because its risk to reward ratio decreases. Knowing its base is insufficient to win, further reducing it does not risk defeat — only greater defeat — while augmenting it offers victory’s only chance. 

Who are these base supporters? The reliable regulars — those who vote, and vote for your party, in high percentages. Liberals and conservatives are perfect examples. Liberals accounted for 20 percent of voters in 2010 and voted 90 percent Democratic. Conservatives accounted for 42 percent of voters in 2010 and voted 84% Republican. 

The center’s Independents are not only the hardest to get, but to retain. In 2008, they voted 51 percent for Democrats; in 2010, they voted 56 percent Republican.

The risk of “playing to the center” is real. In 1988, Bush I made his “no new taxes pledge.” In search of a bipartisan deficit reduction deal — the kind so many pundits profess should be in reach today — he broke that pledge. It cost him, and his party, dearly. He did not gain the center, he lost the right. And the election. 

While the risk is real, the reward of “playing to the center” can be illusory — not just in practice as in 1992, but in theory. Despite polls showing “undecided voters” right up to Election Day, in reality they may never decide on a candidate. They may decide to not vote at all. 

Going into a given election, the absolute number of votes needed to win is unknown. What the parties do “know” is that of all the potential voters out there, their base comprises those on whom they can most depend. The closer the election, the more the contest becomes about who wins the most of these. 

It is a political curiosity therefore that the closer the election, and the more its outcome appears to be dependent on the center, the more the two political parties are driven from the center. It is not simply ideology, and it certainly is not irrational. It is economics: the center’s incremental cost increases as the number of voters in the center decreases. 

For those imagining that America’s tight political balance is pushing it toward compromise, it is actually serving to pull it further apart.