He is, in these final weeks, like a boxer, hopelessly behind on points in the 14th round, flailing at the air, jabbing, hooking, hoping that a punch will connect.

None has. And John B. Anderson knows it. His two major party opponents hardly notice he is in the ring.

But there's little else to do, so he keeps swinging, careening off the ropes of American politics, hoping for the right opening.

At times, almost always on some college campus, he is taken over by a rush of frenzied eloquence. Bathed in the klieg lights of the television networks, he looks for a brief moment like a genuine contender.

His jaw is strong, his back straight, his thick hair a glistening snow white. Sweat rolls off his pale face. His voice pleads;

"Dare to send a message to the two traditional parties. Take a chance with your vote. Add your voice and your vote to that great movement of American people that is going to revitalize our politics, that is going to rehumanize our economics, that is going to give new life to our foreign policy, and new hope to all of America."

Whether it is here at Ohio State or in New Haven, Chapel Hill or Madison, the crowd is suddenly his. Thousands of students jump to their feet, stomping, clapping, shouting, "Anderson, Anderson, Anderson."

But then the moment passes. The bright faces of youth fade in the shadowy realities of politics. Here Anderson's standing drops with almost every public opinion poll.

Here he is a lonely figure shadow-boxing in the corner of presidential politics. Here, his only real hope is that the two guys in the center ring, Ronald Reagan and President Carter, will pound one another to the mat.

With only three weeks to go before Election Day, it is a frustrating place to be. In these circumstances, politicians, like journalists, search the sports pages for the proper metaphor.

"I'm getting down to the wire," the independent candidate said in an interview. "It's like a runner who reaches the final turn and the tape is almost in sight and you've really got to the final commitment. I want to be low-key and relaxed and Will Rogerish like people say you should . . . but a certain urgency takes over and I can't."

There are those among his oldest supporters who think the time has come for dramatic action: time for Anderson to announce that if he doesn't have enough support to win that he will drop out of the race the week before the election rather than stay in and help elect Reagan.

Early in the campaign Anderson said he would do as much. But now he and his closest advisers completely dismiss this suggestion in public and in private.

"I'll be in this race, God willing, if there's one breath left in my body until Nov. 4," he told one news conference this week. "I will not consider this campaign hopeless until the polls have closed on Nov. 4, and even then I may demand a recount," he told another.

There are practical as well as emotional reasons for Anderson's refusal to give up. First, there's the money question. If he drops out, he would not be eligible to receive the federal campaign funds he now stands to gain if he draws 5 percent or more of the vote. As of Sept. 22, his campaign was $1.2 million in debt. Since then, it has launched an effort to borrow $2 million from supporters with a pledge that they will be repaid with the federal campaign subsidies.

Secondly, Anderson still thinks he has a chance of winning. He considered Carter's decision to reverse campaign tactics last week an admission that the president's campaign was in deep trouble. "Carter's peaked. He is now on the decline and fading fast," Anderson said at one point. " . . . the election is mine to win. It's Reagan's to win."

The latest Washington Post poll gives little evidence to support such optimism. The poll shows Anderson, not Carter, fading. The Illinois congressman drew the support of only 12 percent of the voters in the nation's largest states, most of them East and Midwest, traditionally Anderson's strongest regions in the poll. His highest standing was 17 percent in his home state of Illinois.

Beyond pride, stubbornness and instinct are two, perhaps even stronger emotions in Anderson's refusal to drop out. The first is a sense of obligation to the people who have given their time and money to his campaign.

"He thinks he is the agent of their hopes and it would be a failure of nerve if he quits," said press secretary Tom Mathews.

The other is the overwhelming sense of disdain and anger Anderson holds for Carter in the way he's conducted his campaign. He thinks the president's tactics have proved him morally unfit for office. He charges Carter conducted a "mean and evasive" primary campaign against Sen. Edward M. Kennedy, using the Iranian hostages for political gain. And he accuses the president of using tactics against the Anderson campaign similar to those used by the Nixon campaign against George McGovern in 1972.

Anderson has no particular fondness for Reagan either. He calls him "quaint." He says the Republican nominee has proved one thing -- "old actors never die, they just run for president."

But Reagan and Carter don't appear to notice what Anderson says about them. When he was asked last week in New Haven about the bitterness of his attacks on his two opponents, he told one news conference, "I was just trying to get them to start criticizing me."

They didn't. And everywhere Anderson went the rest of the week he was greeted about questions of being a "spoiler" and signs such as one in New Haven that said, "Vote for Anderson. Elect Reagan. Is this really what you want?" The polls are discouraging. But the crowds are large -- 2,000 at a Liberal Party dinner in New York, 1,200 at a night rally at Yale University in New Haven, 3,000 at a noon rally in Columbus. Then just when everything else seemed hopeless, someone would stand up, like the student at Ohio State Wednesday night, and say:

"I'm glad to see a man like you come along who is real. Who isn't an imitation. Why do you think Jimmy Carter's such a dog and Ronald Reagan is a chump?" This is enough to keep the candidate going into the next round, to the next airport, to the next rally, and to the next week.