DES MOINES, JAN. 30 -- In 1980, George Bush's 2-percentage-point victory over Ronald Reagan in the Iowa caucuses triggered a 25-point swing in five days in New Hampshire primary polls. In 1984, when Sen. Gary Hart (D-Colo.) supplanted Sen. John H. Glenn (D-Ohio) as Walter F. Mondale's main challenger on the basis of Hart's second-place finish in Iowa, Hart surged 18 points and Glenn dropped 9 -- a swing of 27 points -- in one week in New Hampshire.

That history explains why almost all the 13 candidates for the 1988 Democratic and Republican nominations for president are pushing themselves and their organizations to the limit in this last week of campaigning for the Feb. 8 Iowa caucuses.

Whatever New Hampshire chauvinists may claim about the primacy of their first-in-the-nation primary, being held this year on Feb. 16, the Iowa-to-New Hampshire "bump" increasingly looks the size of a mountain, not a molehill.

University of New Hampshire political scientist David Moore has labeled "a myth" the traditional belief that grass-roots organization and face-to-face "retail" campaigning hold the key to the New Hampshire primary. "For both the 1980 and 1984 primaries," he wrote in Public Opinion magazine, "New Hampshire bore all the earmarks of a 'media' state, where local campaigning did not prove to be as decisive in the electoral contest as did national media attention."

The national media are here in Iowa this week, focused almost exclusively on the caucuses where voters will give their first direct judgment on the 1988 field. If history is a guide, the publicity wave that will lift those who win Iowa -- or do "better than expected" -- will be the biggest political event so far in 1988.

That wave threatens the two candidates who have been running out front in New Hampshire polls and have reputedly the biggest and best organizations in that state: Vice President Bush on the Republican side and Massachusetts Gov. Michael S. Dukakis on the Democratic. They are trailing, but not out of the hunt, in Iowa, where Sen. Robert J. Dole (Kan.) leads the GOP polls and Rep. Richard A. Gephardt (Mo.) has moved ahead of Sen. Paul Simon (Ill.) on the Democratic side.

Bush and Dukakis managers can offer a dozen reasons why they can win New Hampshire even if beaten in Iowa. The evidence supports their claims. Reagan turned the tables on Bush after losing Iowa in 1980, and former vice president Mondale's victory in Iowa in 1984 did not spare him from defeat in New Hampshire at Hart's hands.

But after citing some of the reasons that might mitigate the effects of a Dole win in Iowa, Bush national manager Lee Atwater conceded, "We all know there is a bounce. We just don't know how big it will be."

History offers some guide, but the relevant examples are few. The Iowa caucuses have preceded the New Hampshire primary since 1972, but it was only in 1980 that Iowa received media attention of roughly the same magnitude as New Hampshire.

The "rules" that politicians and political scientists interviewed by The Washington Post draw from this brief history are:

Rule One: The "bump" is smallest when there are only two candidates seeking a nomination and both are well-known. President Jimmy Carter's victory over Sen. Edward M. Kennedy (D-Mass.) in the 1980 Iowa caucuses did not move the polls much in New Hampshire, where views of the two men were already well-established.

Rule Two: The "bump" is largest when the field of candidates is big and someone unexpected comes zooming out of the pack and establishes himself either as the candidate to beat or as the main challenger. Bush did the former in 1980. By edging Reagan by roughly 3,000 votes in Iowa, he moved from 19 points behind to 6 points ahead of Reagan in the next five days' New Hampshire tracking polls by Reagan pollster Richard Wirthlin.

Hart did even better in 1984. He finished a distant second to Mondale in Iowa, drawing only 16 percent of the caucus votes. But Glenn, who had been perceived as Mondale's main competitor during the preelection year, was fifth. "It was absolutely devastating," Glenn campaign spokesman Greg Schneiders recalled last week. "Glenn's viability depended on his retaining the role of being the alternative to Mondale. As soon as he came in fifth in Iowa, he lost any legitimate claim."

Washington Post-ABC News tracking polls in the week following Iowa saw Glenn drop from 23 to 14 percent, Hart climb from 12 to 30 percent. On New Hampshire primary day, Hart's continuing surge gave him a 40-to-29 percent victory over Mondale, with Glenn at 13 percent.

Rule Three: The shorter the time between Iowa and New Hampshire, the bigger the "bump." In 1980, when there was a five-week interval, tracking polls showed the maximum "bump" about five to eight days after Iowa. But Reagan had time to reverse it by assiduous campaigning and by stellar performances in two last-week debates that became the dominant media events. In 1984, by contrast, there were only eight days between Iowa and New Hampshire, as there are this year, and no intervening events superseded the impact of Iowa.

Rule Four: Iowa indelibly stamps some people as losers. In a 1987 book on the New Hampshire primary, significantly entitled "Media and Momentum," William G. Mayer of Harvard said, "The 'winnowing' function -- the process by which a large, multicandidate field is narrowed to two (or at the most three) top contenders -- is now performed almost entirely by the Iowa caucuses. New Hampshire propaganda still likes to portray itself as The Great Winnower, but, in fact, there is no evidence that it has actually played this role in any election since 1976 . . . . The New Hampshire primary, on the other hand, has become the first major test of strength between the two candidates who will, in all probability, fight it out through the rest of the primary and caucus season."

As evidence of Mayer's thesis, the four trailing Republican candidates in the 1980 Iowa caucuses got barely one-quarter of the New Hampshire vote among them; the six trailing Democrats in the 1984 caucuses split less than 30 percent of the New Hampshire vote.

Applying these "rules" to the 1988 situation may be risky, but it does not prevent it from happening. The "loser's label" law that anyone outside the top two in Iowa has trouble breaking out of single digits in New Hampshire seemingly threatens all those who are beaten there, and especially the two candidates -- Sen. Albert Gore Jr. (D-Tenn.) and former secretary of state Alexander M. Haig Jr. -- who have abandoned any serious efforts in Iowa, in Gore's case because he is concentrating on the South and in Haig's because he has put his limited financial and organizational resources into New Hampshire.

The test of that rule may come from Hart, who reentered the race too late to do much organizing in Iowa but has a residue of high name identification and a cadre of loyal supporters in New Hampshire.

The eight-day gap between Iowa and New Hampshire should increase Iowa's carryover effect. "The shorter the time, the higher the bounce," said political scientist Nelson W. Polsby of the University of California-Berkeley, coeditor of "Media and Momentum." But there will be televised debates in New Hampshire shortly before the primary -- Democrats on Feb. 13 and Republicans on Feb. 14 -- and, as Moore said, "If somebody does something notable there, it could create its own momentum, with nothing to break it."

The rule that Iowa's blessing is particularly valuable to unknowns in a multicandidate field seems made-to-order for this year's Democratic race. Gephardt, Simon and former Arizona governor Bruce Babbitt -- the three Democrats who at times have seemed capable of beating Dukakis in Iowa -- lag 15 to 25 points behind him in New Hampshire in name identification and from 26 to 30 points behind in support.

"For anyone in our position," said Simon spokesman Terry Michael, "an Iowa victory would be very significant." William Carrick, Gephardt's national campaign manager, agreed that Iowa "will probably define who the clear challenger is to Mike Dukakis . . . . And the way the Boston television stations are covering this race {in Iowa} makes it even more important."

Predictably, the Dukakis camp is trying to minimize the stakes in Iowa. Charles Campion, a veteran of the Mondale campaign now working for Dukakis, said, "The dynamic is different from 1984. Dukakis is not the national front-runner so there's no question of New Hampshire voters thinking they're being asked to rubber-stamp a preordained decision. And he is so well-known in New Hampshire, his positives are strong and his negatives low in every poll, it will be hard for people to change their opinions quickly."

Nonetheless, Campion said, "Iowa will set the dynamic of who is in it with him {Dukakis} in New Hampshire, because right now New Hampshire doesn't know who it's dealing with."

The converse is true of the Republican race, some think. Bush strategists argue that because Dole is already well-known, he would gain relatively less from the victory he expects in Iowa. "Bob Dole can't be a phenomenon coming out of Iowa," argued Atwater, Bush's national campaign manager. Another Bush strategist noted that "the Iowa results will furnish a substantial portion of what New Hampshire voters know about most of the Democratic candidates; they will add only marginally to their knowledge of Bush and Dole."

Wirthlin, now polling for Dole, concedes some of these points. "With Bush and Dole running 1-2 in both these states," he said, "a win by either wouldn't upset expectations to the same degree as Bush's win in 1980."

Nonetheless, an Iowa victory is the keystone of Dole's strategy. His national chairman, William E. Brock, said, "It would tell people in New Hampshire and across the country that George Bush is not invulnerable. It would get more of them to listen to what Bob Dole says, what he thinks and what he feels . . . . "

Even more than Dukakis' managers, Atwater insists that Bush "can survive an early loss, because we are running a national campaign. A Bush victory in Iowa makes him the nominee; a Dole victory just lets him play another day."

But history suggests the Day After Iowa can be very different.Staff researcher Colette T. Rhoney contributed to this report.