ANYONE WHO HAS spent any time in North Carolina in the last year may be excused for forgetting that there is a presidential election on and for supposing that the only contest that matters is the race for U.S. senator. In terms of dollars spent and psychic income invested, that contest overshadows anything else that is happening, politically or otherwise, in that state -- or just about anywhere else this year. It's the most expensive Senate election in American history: the two candidates, who have known for at least four years that they would be running against each other, have raised a total of $21 million so far -- and responses from the direct mail are still flowing in.

The bigger spender is Sen. Jesse Helms, who has refined the arts of direct mail and of negative campaigning into a strong alloy. Mr. Helms has raised and spent more than $12 million. His opponent, Gov. Jim Hunt, initially budgeted $5 million to oppose him. But so intense is the feeling about this contest that he's been able to raise more than was budgeted both in the state and through nationwide direct mail, to the tune of $8 million.

This money has enabled the candidates to conduct something like the kind of old-fashioned debate candidates used to engage in on a single platform. The basic message of the two campaigns, however, is revealingly different. Mr. Helms emphasizes his support up and down the line for Ronald Reagan (naturally failing to mention the times he has made life miserable for administration officials). But unlike Mr. Reagan, he is not running a campaign that draws on the optimism and confidence that is increasingly prevalent today. Instead, Mr. Helms voices the same sour, negative message that he has throughout his lengthy career, that they -- liberals, Washington bureaucrats, civil rights activists; he's never quite clear just who -- are doing terrible things to America. Just in case voters don't get the message, Mr. Helms made a point of opposing the Martin Luther King holiday.

Mr. Hunt bases his campaign on his eight-year record as governor. Walter Mondale is running way behind in North Carolina; the state has one of the nation's lowest unemployment rates, a booming no- union economy, an aversion to higher taxes. Mr. Hunt's message, like Ronald Reagan's, is essentially positive: that North Carolina has moved ahead economically and in a "progressive" direction.

Who's going to win? Mr. Hunt had an initial lead; then Mr. Helms went out in front after a barrage of early negative TV ads; this fall the race has been seesawing. It is one contest that almost everyone thinks matters, not just a battle of Republican versus Democrat or progressive versus conservative, but of positive versus negative, a complainer versus a doe.