Harriett Woods bubbles warmly, like Welsh rarebit, when explaining all the nice things she will do for everyone if she defeats Republican Sen. John C. Danforth. But her policy pronouncements are as airy as cotton candy.

Woods, 55, a state senator, is earnest and ingenuous and brimming with the wish to do good works. But her campaign, when not featuring ad hominem attacks, consists of sustained wishful thinking -- a stark unwillingness to face choices. Hence, her campaign, with its strategic silences about real dilemmas, illustrates the grinding difficulty of government in this decade.

She demands "sharp reductions" in the federal deficit. But she says no cuts are necessary in social programs -- and she favors various new programs, and subsidies for industries.

Reading, earnestly but confusedly, from a badly typed page that is a tossed salad of numbers, she promises huge defense cuts. But her numbers are for a fiscal year for which appropriations will be finished before the next Senate convenes. She endorses 6 percent growth in defense spending. But the president's request for obligational authority (which is what Congress can control, year-by-year) for the next four fiscal years comes to less than 7 percent growth. The difference between her number -- did she pick it at random? -- and the president's would not alter the country's economic course.

Her answer to the Social Security problem is to deny that there is a serious problem. Well, if you make sufficiently unrealistic assumptions (about economic growth, employment and demographics), any problem can be made to disappear, on paper. But Missourians must wonder: if, as sober Democrats and Republicans agree, Social Security needs help, who is most apt to restore its health -- a doctor who treats ailments seriously, or one who just prescribes wishful thinking?

Woods is not cynical, but she does not have an inkling of an idea how agonizingly difficult are the decisions confronting senators. She lives in a mental world without costs, where numbers, when needed, seem plucked from thin air.

In 1980, some sincere but dangerously ill-informed Republicans won by claiming that the budget could be balanced painlessly, by just eliminating "waste, fraud and abuse." In 1982, some liberals are selling a similar delusion: economic health requires just slashing defense, closing some "loopholes," and borrowing money while waiting for demographic trends to make Social Security healthy.

The pell-mell pace of a candidate's life makes thought difficult, and a challenger often starts from a low base of information. But we dare not let that become an excuse for a kind of campaigning that does not treat voters as adults capable of comprehending hard choices. Woods has been at this for a year. It is October, America's month of seriousness. If America's problems are as serious as she says -- and they are much more serious than she seems to understand -- we cannot afford to settle Senate contests with slapdash promises and name-calling.

Woods' television ads contain unexceptional sentiments ("There is something wrong. . . . It's not right. . . . I'd like to change it. . . .") and nothing else. She harps on the fact that Danforth, 46, is wealthy, calling him "aloof," an "aristocrat" who has a "patrician, do-good-but-we'll-make- the-decisions" style. Does she propose to be a senator who does not make decisions? Does she blame him for having wealthy parents?

She is properly proud of having campaigned for Stuart Symington, a fine senator from Missouri for four terms. Symington was more patrician, in manner and background, than Danforth is. If Missourians have forgotten Symington, there may be political mileage in Woods' George Wallace-style rhetoric. But if she had her way, the likes of Franklin Roosevelt (and many others, from George Washington to Adlai Stevenson and John Kennedy) would be excluded from public service.

"Aristocrat"? I have joined Jack and Sally Danforth at a Jerry Jeff Walker country-music concert, where "aristocrats" were not admitted. "Aloof"? Fiddlesticks! I have seen him striding through one of Washington's stuffiest establishments wearing a crimson Cardinals' baseball cap.

The Senate is like a lot of institutions: 20 percent of the members do 80 percent of the work. Danforth, a leader on the committee (finance) with the most talent and most complicated business, is among the 20 percent. If you asked Danforth's 99 Senate colleagues to list the 10 most respected senators, only one name probably would appear on every list: Danforth.

Some of the weakest senators were elected in 1980 on Reagan's coattails. It would compound the institutional injury were any of the strongest to lose in 1982 because of a Reagan undertow. Danforth is leading. The show-me state can show the nation that the times are too serious for unserious campaigning.