The danger of political loss attending President Carter's retreat from campaign promises in the Wheat Belt is that the broken promises coincide with a Wheat Belt recession of portentous political dimension.

The President's year-old pledge to give wheat farmers a level of prices supports "at least to equal production cost" might be passed over as standard campaigned hyperbole if wheat prices were now firming and farmers contentedly purring.

Instead, a little-noticed survey by the Department of Agriculture show that in mid-spring three of six major wheat states - Kansas, Nebraska and Oklahoma - where in "very severe" financial straits; the other three - Colorade, North Dakota and South Dakota - were in "severe" financial situation.

This largely overlooked report makes sinister reading: Of 32,000 bank borrowers surveyed in Kansas during April, where almost all loans are linked to the wheat economy, 3,200 "cannot repay" their loans and 11,600, or 35 per cent,are either compelled to refinance their indebtedness or "dispose of their assets."

Consequently, wheat farmers are not purring contentedly. On the contrary, added to the normal political grievance spreading across the lush soils of Kansas is the special fury of a voter scorned that comes from this fact: Thousands of wheat families and other rural voters reversed age-old Republican voting habits last November to support Jimmy Carter, apparently on the theory that a peanut farmer was natural ally of a wheat farmer.

The degree of this crossover, with its potential of a huge voter harvest by Carter in 1980, has apparently been missed by the White House. Otherwise, the President might not have walked away so quickly from his campaign talk of a $3 price support for wheat (which he set instead at the old $2.25 level).

Likewise, Secretary of Agriculture Bob Bergland, who is perceived out here as an amiable White House messenger boy, would probably have fought harder for his farmer constituency against Carter's strong budget-balancing policies.

The switch of voters from Republican in 1972 to Carter-Mondale last November, as reported in a confidential poll by respected political pollster Robert Teeter, was much heavier among rural than city voters. In Nebraska, a major wheat state, Teeter found the pro-Carter switch in the farm vote running 6 percentage points ahead of the pro-Carters switch in towns and cities.

Even more astonoshing was Ohio. Republican farm defections to Carter in Ohio began worrying party leaders well before the election, but Teeter's 1977 county-by-county analysis shows the depth of that defection: a 19-percentage-point decline in the Republican presidential vote, as contrasted with a mere 9-point decline in the cities of Ohio.

"The surprising loss of Ohio [by Gerald Ford] can be attributed to the unique impact that Carter had in the rural areas," Teeter's unpublished poll reported. "These [voting] changes produced the unusual pattern of a Republican presidential candidate receiving a higher vote from Ohio's metropolitan area (46 per cent). In 1972, Nixon ran 7 points better in the rural than the metropolitan counties of Ohio."

Likewise, Teeter found that in the "contribution ratio" (the share of the total republican vote) in Wisconsin - a major farm state - rural counties contributed areas. That elevted Carter almost 10 points ahead of the 1968 performance in rural Wisconsin of Hubert Humphrey, long a farmer hero.

What this means is that the farm states saw something special in peanut farmer Jimmy Carter. Indeed, Teeter found that the only offset to the surprising strength of Carter and his running-mate, Mennesota's Walter Mondale, in 11 farming states was Kanasas Sen. Robert Dole. The counties in which Dole campaigned last fall showed a consistent 2-point lag in their swing to Carter-Mondale compared with counties where he did not campaign.

Some politicians suspect that Carter has consciously ignored these pro-Carter sympathies in cutting farmers out of his shrinking pie of federal subsidies. Others blame it on simple White House ignorance of Wheat Belt politics. Whichever it is, the swing back to the Republicans in the Wheat Belt ison in earnest, fueled by the fury of the scorned.