The Democratic and Republican parties used to promote skilled coalition builders. Now the American parties have come to resemble the ideologically coherent European ones.

The Democrats talk and look like a conventional liberal party (some liberals, who represent, at most, 30 percent of the country, are disappointed because President Obama hasn’t ushered in a Huffington Post paradise). Meanwhile, many Republicans flock to Herman Cain or Newt Gingrich because they are more interested in having a leader who can take on the mainstream news media than in having one who can plausibly govern. Grover Norquist’s tax pledge isn’t really about public policy; it’s a chastity belt Republican politicians wear to show that they haven’t been defiled by the Washington culture.

The era of the two moons is a volatile era. Independent voters are trapped in a cycle of sour rejectionism — voting against whichever of the two options they dislike most at the moment. The shift between the 2008 election, when voters rejected Republicans, and the 2010 election, when voters rejected Democrats, was as big as any shift in recent history.

Sometimes voters even reject both parties on the same day. In Ohio this month, for example, voters rejected the main fiscal policy of the Republican governor. On the same ballot, by 31 points, they rejected health care reform, the main initiative of their Democratic president.

In policy terms, the era of the two moons is an era of stagnation. Each party is too weak to push its own agenda and too encased by its own cocoon to agree to a hybrid. The supercommittee failed for this reason. Members of the supercommittee actually took some brave steps outside party orthodoxy (Republicans embraced progressive tax increases, Democrats flirted with spending cuts), but these were baby steps, insufficient to change the alignment.

In normal circumstances, minority parties suffer a series of electoral defeats and then they modernize. But in the era of the two moons, the parties enjoy periodic election victories they don’t deserve, which only re-enforce their worst habits.

So it’s hard to see how we get out of this, unless some third force emerges, which wedges itself into one of the two parties, or unless we have a devastating fiscal crisis — a brutal cleansing flood, after which the sun will shine again.