In schools, libraries and even some private homes, Iowa residents will gather tonight to start the months-long process of selecting delegates to the Democratic and Republican National conventions.

The Iowa Caucus--a national presidential campaign institution since 1972--will take place in about 2,100 locations across the state. About 200,000 voters are expected to participate.

Though Iowa is small-- states like California and New York will send many more delegates to the conventions and are better indicators of how a candidate will fare nationally--it is the first real test of candidates' popularity and their ability to organize groups of voters.

Iowa can help or hurt candidates in several ways.

The first indicator of a possible turn-around in the campaign is if a candidate surpasses all expectations in Iowa, garnering more support than the polls currently indicate. This happened in 1976, when Jimmy Carter, a virtual unknown nationally, catapulted himself into the lead and, eventually, into the Democratic nomination. Since 1972, all presidential nominees have finished at least third in the caucuses.

As of yesterday, polls suggest that both Republican and Democratic frontrunners, George W. Bush and Al Gore '69, have commanding leads in the state.

But the other candidates have stepped up their campaigns--even though they know they will not gain the most votes.

While Bush is the first choice of Iowa voters, polling about 42 percent, publisher Steve Forbes runs second at 20 percent. He hopes a strong finish will give his campaign organization momentum and help to draw more conservative Republicans to his fundraisers. Forbes has run a barrage of television ads in the last few days, accusing Bush of reneging on a plan to cut Texas taxes.