Parties now and again face troubled times when they go down in the flames of infighting or overreach, subside and recoup while the other takes over, and then they return with new strength.
But what happens if they both manage to blow up at once, when neither seems willing or able to govern and trust in them takes a dive?
For one thing, it makes predicting things difficult, including which party is more likely to fail in the 2014 midterms — the one facing a war between its purist and practical factions, or the one chained to the anchor of Obamacare, which is pulling it under the waves?
In retrospect, it's hard to blame Democrats, with their charismatic young leader and their monstrous leads in both houses of Congress, from trying to go for the great unrealized dream of their party — health care for all.
What they can be blamed for is the how, when and where they did it, which broke all the laws of common sense and political prudence that were carefully built up by time.
Franklin D. Roosevelt, for example, waited two years to introduce Social Security, after the Great Depression's economic free-fall had been stabilized; Obama waited four months for health care, going for it while unemployment was rising.
Roosevelt took care to build up broad and bipartisan backing; Obama took his sliding poll numbers, Republican angst and stiffening resistance as cause to barge ahead. Two huge election reverses (in Virginia and New Jersey) did nothing to stop him.
A third defeat (in Massachusetts) designed explicitly to stop his new bill from being enacted, drove him to a tactic of enactment by loophole that drove his opponents into frenzies of rage.
"Great measures should not be passed by narrow majorities" was the time-honored rule, while Obama’s was, "Let’s pass a huge law with majorities going against us, and see how it all will work out."
It worked out with a landslide election that gave the House of Representatives, 30 state houses and more than 700 new state legislative seats to the Republicans, who created new obstacles to the law he was passing and crippled the rest of his term.
He saved his own skin only by delaying implementation till 2013, so that his re-election fell into the lull between crises when the issue, since nothing new happened, seemed to fade from the scene.
But the Oct. 1 launch, with the Internet chaos, the rises in cost and the loss of coverage for millions, brought it all roaring back.
In a matter of days, Democrats, thrilled at watching the shutdown consume Republicans, suddenly realized their house was on fire, too, and that, like the Republicans, they had set the blaze all by themselves.
Ah, the shutdown. No such fun had befallen the Democrats since 2008, when the financial collapse swept away the small early-September lead John McCain had established and tipped the election into their lap.
Not in their dreams could they have invented Texan Ted Cruz, who talked congressional Republicans into a shutdown they were certain to lose, then blamed them for losing, said they had won when their favorability rate dropped to 28 percent and threatened new shutdowns, perhaps in the hope of dropping it down to 18 percent.
Many Democrats knew passing health care was a mistake, just as Republicans knew the shutdown would be a disaster, but they were helpless to rein in their zealotry factions.
Had they done so, they knew the zealots would be claiming forever that the bill and the shutdown were wonderful projects, and would have brought endless acclaim.
With friends like themselves, they barely need enemies. But have they run out of feet into which to pump bullets? The chances are, probably not.
Noemie Emery, a Washington Examiner columnist, is a contributing editor to The Weekly Standard and author of "Great Expectations: The Troubled Lives of Political Families."