Having finally adopted a bipartisan budget deal, members of Congress now have to translate its broad outlines into detailed spending bills — and raise the debt limit enough to let the Treasury keep those commitments. You might think that the agreement would make both of those tasks easier, but the last such deal didn't stop the parties' near-incessant squabbling. Lawmakers have little hope of avoiding another politically damaging shutdown or an economically ruinous default unless they absorb the lesson that led to this month's compromise: They can't make progress unless they stop trying to force the other party to give up its core beliefs.

Congress has gotten remarkably little done in the last four years as it has lurched from one partisan showdown to another. Both sides have sounded like broken records, with Democrats arguing again and again that government should raise spending and revenues, and Republicans seeking relentlessly to cut taxes and spending. Even when they agree that something must be done — for example, that entitlements should be reined in to slow their growth — they disagree sharply over how to do it.

That's why the budget deal negotiated by Sen. Patty Murray, a liberal Democrat from Washington, and Rep. Paul D. Ryan, a conservative Republican from Wisconsin, was both improbable and instructive. The proposals their chambers had passed several months earlier embodied the parties' dueling ideologies, and so diverged wildly over spending levels, tax rates and entitlements. To strike a compromise, Murray and Ryan had to find new ways to split the difference in their proposed spending limits that didn't violate Republicans' opposition to tax hikes or Democrats' refusal to cut aid to the needy. And so they did, agreeing to provide more discretionary spending in exchange for less mandatory spending, some fee increases and trims to military pensions.

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In other words, Murray and Ryan ventured out of the trenches their parties have occupied for the last four years. Yet some members — particularly Republicans affiliated with the tea party or facing primary challenges from that wing — remain dug in, unable to recognize the reality of divided government. Another round of damaging brinkmanship could come early next year if the House GOP insists on cutting entitlements as a price for raising the debt ceiling, on the absurd theory that they can force Democrats to abandon their principles simply by giving them the right ultimatum.

The GOP is right to worry about the trajectory of Washington's finances, just as Democrats are right to worry about the stubbornly high unemployment rate and the stagnating fortunes of the lower and middle classes. And some of the problems Washington faces may be too big to solve with anything short of a "grand bargain" on taxes, spending and entitlements. But such a deal seems like a bridge too far in this political environment. The sort of incremental compromise that Murray and Ryan struck keeps the process moving and the government functioning, which is far better than the alternative.