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.

Bush's closest competitor on a national scale, Arizona senator John R. McCain, has largely ignored the caucus, and has been relegated to the third tier of candidates along with Alan L. Keyes '72 and Gary Bauer, who have four percent of voters' support between them. McCain's decision not to support ethanol subsidies, which Iowa farmers rely on, has made him unpopular in the state, though the candidate claims the subsidy is unnecessarily protectionist. Bypassing Iowa has allowed McCain to spend his time and money in New Hampshire, where most polls show him tied with Bush.

In the Democratic contest in Iowa, Gore leads Bradley by 56 percent to 28 percent, according to the latest poll. Bradley has spent $2 million dollars in the state. His campaign hopes for a stronger showing than the predicted by the polls. A stronger-than-expected showing in Iowa could give Bradley a "bounce" in New Hampshire's primary nine days from now, where he polls evenly against the Vice President.

Yesterday, Bradley received the endorsement from the Des Moines Register, the most influential paper in the state.

For both Bradley and McCain, the decision whether or not to canvas Iowa also involves their belief in the state's influence on later primaries.

Bradley is hoping for the kind of surprise victory that the former Georgia governor Carter earned in 1976, a victory which helped him gain legitimacy, and may have given him the necessary name-recognition to win the nomination.

McCain is operating on the opposite premise that the Iowa caucus has little influence on the rest of the primary campaign, and that the New Hampshire primary is a better indicator of overall strength. His case study would be George Bush, who in 1980 won the Iowa caucus but lost the presidential nomination, and in 1988 lost the caucus and won the nomination.

Evidence for the "bounce" theory can be gathered from the 1980 caucus, where Sen. Edward M. Kennedy '54-'56 (D-Mass.) got 31.2 percent of the vote in Iowa against Carter's 56 percent, and Carter went on to take New Hampshire by a wide margin. On the other hand, in the same year Bush won the Iowa caucus, the eventual Republican nominee (and subsequent president), Ronald W. Reagan, took New Hampshire only eight days later.

Despite all the hype about Iowa, the true test for the candidates won't be for at least a month. On March 7, also known as "Super Tuesday", 15 states, including New York and California, will have their primaries.