A strangely bland Sen. Edward M. Kennedy failed to generate the excitement that his supporters here prayed for from his five-day swing through rural Iowa -- a failure that menaces him in the Jan. 21 Iowa Democratic caucuses and clouds his entire challenge to President Carter.

Kennedy's late-starting, smoothly functioning Iowa organization has nullified Carter's head start in the state's metropolitan areas. But to counter Carter's advantage planted in rural counties by his 1976 saturation campaign, Kennedy needed a galvanic effect from his swing -- to persuade county Democrats suspicious of the Eastern seaboard liberal to devote a night in the dead of winter to opposing their party's incumbent president.

Kennedy did not approach that goal. In toning down his delivery to small-town Iowa standards, he became bland. Be steering clear of long-held liberal positions, he lost conviction. Amid central Iowa's snows, occurred the spectacle of a boring Kennedy campaign for president.

Even so, Kennedy's metropolitan strength, plus lack of enthusiasm for the president, may prevent a Carter runaway; bad country roads might even sneak Kennedy ahead. But whatever happens here Jan. 21, Teddy among the Hawkeyes showed he still presents no politically effective rationale for challenging the president.

When Kennedy arrived in Iowa Jan. 7, there were signs that the absent Carter's Iranian-spawned popularity, sustained by Afghanistan, was fading. Carter operatives confessed sighting a Kennedy's resurgence, fueled by two presidential actions: the Iowa debate cancellation and the Soviet grain embargo.

Kennedy strategists concurred, but called for help from their man. United Auto Workers political operative Chuck Gifford told a friend that Kennedy had to electrify rural audiences. Polk County (Des Moines) Supervisor Tom Whitney, founder of Iowa's draft-Kennedy movement, was more specific about what the candidates must provide to justify challenging the president: vigorous denunciation of Carter's grain embargo, more vigorous positions on Iran and Afghanistan. The Kennedy swing drew full to overflowing audiences in Carter country. But many were there just to glimpse that glamorous and tragic couple, Ted and Joan Kennedy. An example: Carroll, a socially conservative German-Catholic town hostile to Kennedy because of Chappaquiddick and abortion. Out of more than 400 who traveled icy highways to see Kennedy, his managers had hoped at least 200 would sign Kennedy pledge cards. The total was 175 -- pretty good, but possibly not good enough.

However, the real question is whether Kennedy energized those 175 signers to attend caucuses for him. He certainly did not follow Tom Whitney's advice on Iran and Afghanistan. The senator and his strategists remain paralyzed on how to criticize the president in time of crisis. While telling audiences that "we have been lurching from crisis to crisis," Kennedy quickly changed the subject.

Nor did he frontally attack the grain embargo, as Carter backers had expected. Kennedy might have been thrown off by public criticism of his stand from an important Iowa supporter, Farmers Union leader Lowell Gose. The next morning, with prices dropping in reopened commodity exchanges, Kennedy ignored the embargo in his first stop and addressed it but sluggishly the rest of the day.

What he did say wa subdued and conversational, not even faintly reminiscent of Kennedy's characteristic stentorian, dramatic style. Criticized for shrillness in early visits to Iowa, he was cautiously restraining himself. When he briefly raised his voice in assulting the lack of "respect" for the United States today, he stopped abruptly, with this sheepish apology: "I'm getting all exercised here."

Kennedy surely did not represent himself as the liberal alternative to Carter (and did not even mention his famous health care program). But while forsaking the left, he could not embrace positions to Carter's right. When questioned in Oskaloosa about defense spending, he replied: "Less [spending] is not better. More is not better. Better is better."

Such fence-straddling soured a home builder, a Democratic voter for 30 years looking for a more forceful alternative to Jimmy Carter. He attended Kennedy's Indianola stop uncertain whether to support Kennedy or a Republican. After hearing Kennedy, he is now undecided between George Bush and Howard Baker.

The more frequently heard criticism, against both Carter and Kennedy, in non-militaristic Iowa is inflation. Pam Heiskov, a 37-year-old farm wife from Knoxville who sells real estate on the side, was concerned that "Kennedy likes too much government" but had not ruled him out. After hearing Kennedy, she complained that he had not squarely addressed inflation. Heiskov probably will not attend her Jan. 21 precinct caucus -- one of the voters Kennedy failed to win as he traveled through Iowa.