DES MOINES, JAN. 7 -- The final big buildup occurred almost overnight.

Former Arizona governor Bruce Babbitt brought in 50 "fresh troops." So did Sen. Paul Simon (D-Ill.). Rep. Richard A. Gephardt (D-Mo.) countered with 45 new faces; Massachusetts Gov. Michael S. Dukakis quickly trained 30 new recruits and dispatched them to the field.

Suddenly, after months of dull preliminary skirmishes, there is a sense of urgency in the long Iowa presidential campaign.

Military metaphors are on everyone's lips. There is talk about "hand-to-hand combat," "body counts," "the arms buildup" and "drawing a little blood."

"This is real war," one is told at Vice President Bush's campaign headquarters. "There is a rumor that Babbitt parachuted 60 more people in last night," someone whispers at Gephardt's headquarters a few blocks away. "We're fighting in the trenches now."

"It's like the arms race. You don't want to get outgunned. So everyone is bringing in as many people as they can," said Pat Mitchell, Simon's Iowa coordinator.

The candidates have been visiting Iowa regularly for more than two years. As of Jan. 1, Democratic hopefuls had spent 508 days in the state; Republicans 296 days.

For all the time, work and money spent here, both races are uncertain with only a month to go before the Feb. 8 precinct caucuses. Conventional wisdom has two "favorite neighbors" -- Kansas Sen. Robert J. Dole (R) and Simon -- leading their respective contests. Dole's theme line, "He's one of us," plays especially well in this state, and almost every Iowan seems to agree of Simon: "You can trust him."

But wild cards in both races -- What's the size of Pat Robertson's "hidden army" of first-time caucus goers? Can Gary Hart make a showing with high poll numbers, high negatives and no oganization -- make each difficult to call.

Then there is the conundrum of turnout. Today, Democratic and Republican party leaders each predicted record turnouts of at least 20 percent, meaning that the cacuses would be what Howard Baker famously labeled them in 1980: "the functional equivalent of a primary."

But which 20 percent? "Fifty percent of Republican caucus-goers haven't made up their minds if they're going or who they're for yet," said Bush deputy campaign manager Rich Bond. Several Democratic strategists offered a similar assessment.

The first major event of the new political year is a televised debate here Friday night among the six GOP hopefuls sponsored by the Des Moines Register. A similar, two-hour Democratic debate, broadcast statewide, is scheduled for Friday, Jan. 15.

"The debate is like the opening bell of the championship bout," said Bond, who engineered Bush's upset victory in the 1980 caucuses. "I think it's the most important single thing that happens between now and the caucuses," said Tom Synhorst, Dole's Iowa coordinator.

Bush goes into the debate on the defensive about his role in the Iran-contra affair, and with his top Iowa troops executing the classic gambit of lowering expectations about Feb. 8. Bond depicts the goal here as not getting "blown away" by Dole, and George Wittgraf, Bush's Iowa chairman, said the vice president is "hurrying to catch up" to Dole. Bush has been campaigning in Iowa periodically for nine years.

On the Democratic side, the reaction to Hart's high poll numbers -- he's back in the lead, with 25 to 35 percent of the vote, according to three independent polls taken over the past three weeks -- have party leaders muttering in disbelief.

"I can't find a single person for him," said Arthur Davis, a former state party chairman, who is supporting Simon.

"Poll numbers don't mean squat if you don't have an organization," said Teresa Vilmain, Dukakis' state campaign manager.

"He'll wind up with egg on his face caucus night, and I hope it's rotten," said Ken Tilp, president of the Iowa State Teachers Association, which is not endorsing anyone.

The operating theory on how to win the Iowa caucuses is "organize, organize, and get hot at the end."

No one has come up with a sure way to "get hot at the end." But a great deal has been learned about political organizing during the dozen years since Iowa replaced New Hampshire as the first stop in the presidential nominating process.

That's what the buildup this week was all about. It occurred largely on the Democratic side. Republicans rely much more heavily on volunteers and direct mail. Their staffs are relatively small, Bush and Dole each have fewer than 20 people on their full-time Iowa payrolls.

Gephardt doubled his staff from 45 to 90; Simon, who as late as Nov. 1 had an Iowa staff of 37, increased his payroll to 120; Babbitt went from 24 to "70 plus." Dukakis, who has long had the biggest Iowa operation, went from 70 to about 100.

Some of the reenforcements are seasoned veterans. Joyce Banaszak, who first did volunteer work for the Democratic presidential campaign of John F. Kennedy in 1960, temporarily left her three grown daughters and husband in St. Louis to come here to work for Simon.

"Politics is the best game an adult can play," she said. "It is a fascinating process. You get hooked on it. It's like selling, selling an idea, not a product."

Most of the newcomers are far younger -- the vast majority under 25. The '88 campaign has seen the biggest rebirth in student interest since 1972. Most are paid from $400 to $600 a month, barely enough to take care of expenses. They are expected to live in the homes of campaign supporters across the state.

They began arriving last weekend, looking like chilly recruits reporting for boot camp, full of enthusiasm. "For someone just out of political science class like me, this is Mecca. This is it! Iowa is where it's going to happen," said Bob Geolas, 23, of Smithfield, N.C.

Many of the newcomers had never set foot in Iowa before. The first big shock was the subzero weather.

"It's 8 below outside. I'm not one of those people who wants to spend all their life as an icicle," said Tim Driggers, a Gephardt worker who had just arrived from Columbia, S.C.

The recruits were quickly shuttled through training sessions covering such vital subjects as what a caucus is all about, what Iowans are like, how to drive on icy roads, and where to find the campaign's favorite late night watering hole.

Linda San Gabriel, a graduate student at Arizona State, for example, was assigned to work for Babbitt in Clinton County on the Illinois border. "This is strong Simon country so I've got my work cut out for me," she said.

One of the most important items in her campaign kit was a single sheet of paper. It listed how many people attended caucuses in each precinct in the county in 1984 and 1980, how many voted in the 1986 Democratic primary, how many delegates each precinct will elect, and what her goal is in each of the county's 35 precincts. (Gephardt's comparable sheets are more sophisticated, breaking each precinct down to the number of white collar workers, blue-collar workers and Catholics.)

In the next four weeks, San Gabriel's goal is to find 37l people willing to go the caucuses and support Babbitt. To meet this, the sheet tells her she will need 19 people in the second ward in the city of Clinton, but only six in the Elk River precinct. She will be expected to report almost daily on her "body count."

"Everyone is doing pretty much the same thing," said Gephardt field director Jim Cunningham standing beside an Iowa battle map. "This is the most intense organizational effort you'll find in any state in the union. It is very personal, very time-consuming. There aren't any geniuses in it. It is just a lot of long days and one-on-one work in the trenches."