One argument for the "cliff" metaphor is that a lack of action before the end of the year could cause the markets to go haywire and/or erode Americans' confidence about their financial prospects during the holiday shopping season. Shoppers' mood, which had been buoyant in recent months, soured in October, according to the latest Reuters/University of Michigan consumer sentiment index.

Yet it's worth noting that the "cliff" metaphor itself could be partly responsible for all this, since it may very well spook shoppers and investors who might otherwise take into account the likelihood of a damage-limiting deal in January or February. The metaphor would, distressingly enough, gain some legitimacy in part because it makes people think the situation is worse than it is.

"If the reality is we're going to go off the cliff, then we shouldn't get panicky about it," Yardeni said. "We should conclude that we'll survive and that it may even be good for us in the long run if that's the only way to exercise fiscal discipline."