THE CENTER of the free world, in case you haven't noticed it, has been for the past few days -- and will be till next Monday night -- somewhere in the couple of blocks between the Savery and Marriott hotels and the Civic Center in Des Moines, Iowa. Half the nation's satellite dish transmitters will be poised in Des Moines, and a large share of the free world's political reporters will be fanning over all of Iowa's 99 counties, to inform as rapidly as possible a waiting world which candidate is (in George Bush's 1980 phrase) Big Mo and which is No Mo.

Iowa's primacy is a product of the Democratic Party's tinkering with rules: the Democrats try to keep their contests within a 13-week window but, bowing to furious lobbying, allowed the New Hampshire primary to take place three weeks before the window and the Iowa precinct caucuses eight days before that. Does having Iowa go first make sense? There's an argument for starting off with so-called retail contests, in smallish states where voters can see candidates up close and over a long period of time, and once you concede that argument you have to start somewhere. It would be better to rotate the lead-off position, but that would require more tinkering with the system than even the Democrats have been inclined to do lately; and no state is entirely typical anyway. Iowa -- polite, literate, attentive -- is as good a place as any to start off, if you keep the state's quirks in mind. Farm issues, for example, are more important there than nationally, the Democrats are more dovish, the Republicans are more anti-Reagan. Iowa has had the biggest population outflow of any state in the 1980s. But New Hampshire, which comes next, has a booming high-tech economy and the nation's fastest population growth outside the West and South.

A bad blizzard on caucus night would be a blow to Western democracy, but the forecast is for a cold, clear night -- a good time for neighbors to gather in Republican and Democratic caucuses held in schools, churches, living rooms and cafe's in Iowa's 2,487 precincts. There will be a rush to interpret the results, and the networks will try to explain to you how the Republicans conduct a straw poll at the beginning of their meeting, while the Democrats divide into groups supporting each candidate and then elect state convention delegates, with the totals for each candidate being translated in the wee hours by the state party into something called national delegate equivalents.

Don't worry too much about these details: it will be pretty clear who's won something and who's lost. Don't imagine that Iowa is totally representative: only 200,000 or so of the state's 1.3 million general election voters are likely to participate. But do give the Iowa results some respect as the first real word from real voters this year.