They are the boys of winter, America's candidates for 1980, and for months they laid claim to Jimmy Carter's job by taking a hard-line road on foreign policy and a high road on morality. All in the name of leadership.

But Carter's firm embargo on grain and technology sales to the Soviets has caught them in a crush between political rhetoric and geopolitical reality. hAnd, much to the chargrin of their hardline supporters, the response of most of the candidates has been the moral equivalent of meow.

Consider Ronald Reagan.

He is the candidate who has played the role of the hardliner longer than all the rest, and he is standing with his head humbly bowed, in a South Carolina hotel, as retired Gen. Mark Clark delivers himself of an adoring endorsement.

"I've been looking down the sights of a rifle for 50-some years" says the aged general who has just been named Reagan's honorary state campaign chairman. ". . . The only way to keep the peace is to let the Russians know that the only blue chips are the B1 bombers and the Polaris missiles, and that by God, we'll use them if we have to."

Clark steps away from the microphones, and he is asked if he believes that the United States should sell grain or high technology to the Soviets in the wake of their invasion of Afghanistan. "No, absolutely not," says the old general, endorsing Carter's embargo. "We shouldn't sell them anything at all now."

What then, does the honorary Reagan chairman think of Reagan's refusal to support the grain embargo? Clark looks incredulous.

"Reagan said that?" he asks. He shakes his head. "I don't understand it. I -- I don't agree."

The candidates of 1980 have, to a man, set out with plans to make hay while the snow falls, hoping to score well early with a strong showing in the first presidential contest, the caucuses in Iowa. So it is that the Soviet aggression and the Carter response brought them to a political/philosophical dilemma.

George Bush, who was hoping to parlay his outstanding organization in Iowa to an upset victory in the Republican caucuses, was told by his advisers that Republican farmers in Iowa would be strongly opposed to the grain embargo even though Democratic farmers in Iowa would perhaps reluctantly go along with the president's decision, according to sources in the Bush campaign.

Meanwhile, at least one of Bush's advisers, a foreign policy hardliner, urged vehemently that the embargo on grain and high technology had to be supported on the grounds that it was the right policy, and that it was an important public first step for marshaling an internatinal opposition to the Soviet military aggression.

Bush rejected this policy adviser's arguments. "It's fine to talk about sacrifice," Bush said in the Iowa GOP presidential forum. "But if we're going to talk about sacrifice, you don't ask one segment of the economy to sacrifice and you don't impose a program that hurts us more than it does them." s

This was the posture adopted by all but one of the candidates of the Grand Old Party. (Only John B. Anderson, the most moderate and least popular Republican in the polls, was willing to embrace the tough line embargo in Iowa). Haward H. Baker Jr.'s campaign manager, Wyatt Stewart, said in an interview that he believed support of the embargo would politically damage any Republican in Iowa.

For the Democrats, Edward M. Kennedy was quick to oppose the embargo, and Edmund G. (Jerry) Brown Jr. said he supported the embargo while speaking critically of it.

Sen. Strom Thurmond (R.-S.C.) was down in sunny Guantanamo Bay doing a winter season study of military preparedness when his candidate for president, John B. Connally was refining his position on the embargo.

Connally said he opposed the embargo because Carter had not gotten the firm assurances of all allied countries -- in advance -- that they would institue the same embargo. Without this advance assurance, there should be no embargo, he said. Connally, whose tough stance is his trademark, thus would up with a more soft-line position that his colleagues, opposing the embargo not only of grain, but also of high technology -- computers, drill bits and so on.

Thurmond, a super-hawk, issued a statement supporting "the necessity" of the embargo. He did this, according to his aides, without having been aware of the fact that Connally's stand was inconsistent with his own.

Connally spoke of this inconsistency in a candid discussion as his small campaign jet traveled from Macon to Tampa a week ago. Wearing his dark blue three-piece suit, he sat with his smallish, snap-brim fedora still perched atop his largish white-haired crown. He is seeking the votes of Iowa farmers and he already has the campaign cash of the Who's Who of America's big business, which has a sizable stake in future trade with the Soviets. He conceded, as his plane sped through the southern night, that his standing with both groups will benefit from his statements on the embargo.

Connally said that what he believes is not that there should be no embargo, but just that Carter did not go about the embargoing process well. On the question of embargoes, this amounts to: yes, but . . . . However, when spoken on the stump, Connally turns his posture into a no, because . . . . (As in his Iowa debate comment that "I don't think the Iowa farmers should pay the price for the failure of the Carter foreign policy . . .")

Connally was asked if his approach to the embargo was not totally inconsistent with the entire tone and substance of his standard stump speech on the need for America to take firm leadership positions in its Soviet policy and its global trade policy. He paused, and in a moment of candor, he smiled, and the smallish fedora nodded, and he said, "I can't disagree."

The Carter administration's embargo, while founded on solid geopolitical and leadership footing, was nevertheless clumsily executed, thus once more providing administration critics with ammunition that has been returned in salvos.

At the time administration officials rushed to announce their embargo, they did not know who actually owned the embargoed grain (the farmers, the storage elevators or the grain companies?), or where it was in the pipeline. So they talked one day about a series of option to protect the farmer, only to decide in the end to scrap the unrealistic options and buy the crop outright.

It was, as one White House official told Washington Post staff writer Edward Walsh, 48 hours of "policymaking by the seat of your pants."

But if the policy process was the flipside of the brainstorming, the significance of the embargo decision will long be studied by the practitioners of presidential politics.

Politically, the Jan. 11 Des Moines Register poll indicated that Carter may not have been hurt as severely in that state by instituting the embargo as many of the politicians once thought. Of all Iowa adults, 53 percent approved of the embargo and 34 did not; among Democrats alone, this margin swelled to 60 percent approving and 26 disapproving; among Republicans, it narrowed to 47 approving and 42 disapproving; among farmers, the balance tipped with 36 approving and 55 disapproving.

Economically, there were indications that the U.S. farmers would not be hurt to anywhere near the extent that the presidential campaigners of 1980 predicted. On Friday, at the White House, there was quiet rejoicing over statistics showing that the commodities market prices for grain had climbed to where they were before Carter issued his embargo.

And philosophically, the embargo and its aftermath only dramatized the fact that inconsistency often replaces principle in the quardrennial pursuit of the presidency. Philosophy finished second to electability. Perhaps Americans thought they had buried the '70s on New Year's Day. But the hardline boys of winter have brought the ways of the Me-Decade with them, at least through January 1980.