TEN months before the Iowa caucuses, Republican presidential candidates are working restaurants and Rotary Clubs with the avidity of farmers planting spring corn.
In the past two election cycles, Iowa made little difference. Moreover, this year big states such as California and New York have moved up their primaries, and Sen. Bob Dole (R) of Kansas is presumed to be the easy reaper of the prairie vote here.
Still, GOP candidates have spent more than 108 days campaigning in Iowa this year -- and President Clinton came for a conference here this week.
The reason: Iowa, like early bird New Hampshire, can always be a spoiler. If, for example, Sen. Phil Gramm (R) of Texas were to fare well here in the GOP caucuses, he would gain a boost going into New Hampshire.
''In the minds of the candidates, Iowa is still significant,'' says Hugh Weinbrenner, an analyst at Drake University in Des Moines. ''Iowa is first, and the candidates who have done well have had to appear here.''
Iowa will provide a key test, in particular, of the influence of the religious right. Conservative Christians helped Pat Robertson capture second place in the 1988 campaign, and they have grown in prominence since then.
Ione Dilley, the state representative of Mr. Robertson's Christian Coalition, says conservative Christians account for nearly 40 percent of the Republican vote, and currently the bloc is up for grabs. The Christian right ''is not leaning one way or another at the present time,'' she says.
Because they are undecided, argues Washington-based political analyst William Schneider, they have greater leverage. Already, Senator Dole is shifting toward the right, as was seen during a recent stop here when he attacked the immorality of Hollywood.
His campaign has also enlisted one of Iowa's leading Christian conservatives, Steve Scheffler, and hopes to garner at least 37 percent of the overall vote, which is what Dole captured in 1988 when he won the caucuses.
FOR the rest of the pack, the question isn't so much outright victory but how far they will fall behind Dole. In 1984, for example, Walter Mondale, who was expected to win, captured 49 percent. But Sen. Gary Hart (D) of Colorado won headlines by finishing second with 16.5 percent, far higher than expected.
This may explain why Senator Gramm is campaigning so aggressively here. He spends at least two days each month in Iowa, and, according to his campaign chief in the state, Bob Haus, intends to spend up to the Federal Election Commission limits. But so far he has run mostly on economic issues, which Mr. Schneider says isn't winning over the religious right.
''Iowa is a battle for second place,'' Schneider says. ''If someone comes reasonably close to Dole, he could be a significant contender. But the Christian Coalition is irritated with Gramm because he is not stressing social issues. They want to throw their weight around.''
Still, there is a new factor this year that may diminish Iowa's importance: the compressed primary season. More than half the delegates needed to win the nomination of either party will be chosen by mid-March, five weeks after Iowa. That is forcing candidates to rethink campaign strategies.
''The compression means more candidates will last beyond Iowa,'' says Charles Jones, a presidential scholar at the Brookings Institution in Washington. ''If they reach the goal of $20 million by mid-December, intelligent spending of the dough means they could last'' through the intensive first five weeks.
This is already evident in the early campaigning. Over the congressional recess the major candidates made swings through as many as 10 states. The compressed schedule is also making newspapers change how they cover the campaign, which in turn affects the candidates' planning. The media is giving less play to Iowa.
Other Midwestern states, meanwhile, are trying to group together to draw greater media coverage and have more of an impact on the selection process. Wisconsin, Minnesota, Michigan, Illinois, Ohio, and Pennsylvania are considering a ''Big 10'' primary to fall between Super Tuesday and California, which moved its primary forward from June to March 19.
Such a grouping would also undermine the influence of Iowa, and possibly even New Hampshire. ''People got a boost out of Iowa in the past,'' says D. J. Leary, publisher of a Minnesota-based political newsletter. ''Now they will try to get a boost in three or four places at once.''
There is some good news for President Clinton in Iowa. Despite strong Republican gains in 1994, Clinton is running solidly ahead of all GOP challengers except favorite-prairie-son Dole.
''Head to head, Clinton soundly beats everyone but Dole,'' says Mike Peterson, chairman of the Iowa Democratic Party. ''And Dole, who's been a Midwestern senator for 35 years ... is within the margin of error of Clinton.''