Don't worry…

…the Des Moines Register can't poll Iowa, either. OK, maybe they, and their sundry competitors, can spot broad trends. I'll happily accept the revealed wisdom that the proverbial three tickets out of Iowa will go to Senator's Clinton, Edwards and Obama. But the order, or the spread? Nope. The best polls you can get are probably less reliable than a genuinely educated hunch.

I've mentioned the threshold issue and second choices, as well as the intra-personal complications inherent in the caucus system. It gets worse for the pollsters.

The polling we see is almost invariably of a statewide sample, but there's no statewide election in Iowa. It's a precinct by precinct affair and it's simply not practical to examine a sample large enough to reflect variation on the precinct level. Because the real choices are being made in 1,997 distinct constituencies, though, the distribution of support is every bit as, if not more, important as the percentage. That's why, for instance, Edwards' early and consistent attention to rural precincts is an advantage the polls may miss. Caucus attendees in those regions often find their influence outstrips their numbers.

The number of delegates a precinct selects, after all, isn't based on the number of caucus attendees, but is a set number, based on Democratic performance in previous contests, whether there are twenty attendees or two hundred. Again, distribution, which the polls can't measure, trumps percentages, which they, to a degree, can measure.

There's also the question of how the polling samples are shaped to reflect certain assumptions about who is likely to caucus. Some criticism of the Register poll has pointed to the inclusion of an unprecedented number of independents,Republicans and first time attendees in its sample. It's really nothing more than their best guess. Even people who identify themselves as certain to attend sometimes don't. Not everyone will admit that they don't plan to take part on the central stage of American political theater. Not everyone knows what crises or opportunities may present themselves between now and Thursday night.

Nobody knows for sure who'll attend a caucus. Nobody knows for sure what they'll do.

Nope, you can't poll Iowa, and neither can the Register.

All the spin and guesswork's fun to watch, though.