The Wall Street Journal also wondered a bit ago why it’s so hard for the two parties in DC to get along—”the two parties have a hard time even agreeing to disagree,” is the way they put it.

I think they’ve missed a key factor.  Here’s the basis for the WSJ‘s conjecture [emphasis in the original]:

Even when the differences between the two sides seem relatively small—whether, for example, to raise the top tax rate four percentage points for families earning more than $250,000, or whether to make that income level $450,000—compromise is difficult because both sides think important precedents would be set.  Today’s decisions will set the backdrop for broader debates on tax reform and spending later in the year.

When Republicans agreed to raise any tax rates at all, for example, they knew that they had opened the door for a new set of arguments about which rates and at what level.  The question had shifted from whether to raise rates to how—and that’s a significant shift.

It’s more than a significant shift.  It’s a complete surrender of a fundamental conservative principle: lower taxes, which benefits the economy and American citizens; don’t raise them, which achieves the opposite.

For the Democrats’ part, the WSJ says

Similarly, when Mr. Obama said he could accept the idea of reducing entitlement costs by embracing a formula for lowering cost-of-living increases for Social Security recipients, he was setting a precedent as well—a precedent saying that Democrats were willing to consider policies that reduced entitlement spending not just by holding down costs but also by reducing benefits to recipients.

But there is no precedent at all here.  The bit about Social Security was just idle chit-chat—bad faith negotiating.  There is no such thing in the actual deal; Obama accepted nothing related to entitlements, and he set no precedent at all.

Compromise requires a number of factors in order to be possible; among these are a need-driven interest in compromise.  The Republican Party has that interest—indeed, they beg for compromise, any compromise, so they can have a fig leaf of having accomplished something, and they’ve shown they’ll give away the store for the smallest trivium.  The Democrats, on the other hand, have no need of compromise, and so they have no interest in one.  They know that they can get whatever they want out of the Republicans—to the extent they need deal with them at all—because they know the Republicans will fold even on their most fundamental principles.

This is why it’s so hard for the two parties to get along—it’s a strictly one-way affair, with the dominant party having no need of it.