TO AN ENGLISHMAN in this country, it is apparent that political humor is no laughing matter these days.

Anyone who wants to challenge Ronald Reagan in 1984 knows he has to have a barrel full of laughs if he is to keep the American press as happy as the president does with a mere dip of the head, a shy smile and a sense of timing honed by an earlier career in an only slightly different medium.

For example, John Glenn (by his own admission a boring man) has dispatched his campaign staff in search of joke writers.

Walter Mondale, himself not averse to a joke, has a team of experts coming up with one-liners. The rest of the Democratic pack, while trying to talk about substance, look for a way to project themselves as both presidential, and nice and funny.

All of which puts the president at a considerable advantage. If the competition is going to be about who is more entertaining, or who can appear friendliest on TV, Reagan is the clear winner -- a concert pianist in a field of amateurs playing their political spoons.

But I often ask myself how this could happen, when there are so many serious issues to be discussed on which peace, prosperity and perhaps even the fate of the world hinge. I have to conclude that one major reason is that the American press, which is supposed to play a key role in setting the agenda and being a public watchdog, has allowed it to happen. The fact is that the American press gives Reagan an extraordinarily free run, allowing the White House to set the standards by which he is judged. The American media have decided that jokes are an okay way of covering up the president's gaffes.

An example was the reaction of the American press to the Williamsburg summit conference last May. The big news of the summit was not that inflation was at an end or that budget deficits were no more, but that the president of the United States did not shoot himself in the foot.

The Washington Post quoted a White House aide as being pleased that the president had avoided a "disaster," while The New York Times said he had won "high marks" from other world leaders. Specifically, West German Chancellor Helmut Kohl said that Reagan had been "well prepared and well assisted and managed the whole thing with a sense of humor that helped a lot."

Reagan has always fed on the low expectations of him projected by others. One of the rare members of the Washington press to pick up this extraordinary knack is Richard Cohen, the columnist of The Washington Post.

Recalling the coverage of Williamsburg, Cohen said: "You could not imagine the same open-mouthed wonder if, for instance, the subject at hand were Margaret Thatcher. No one would evince either surprise or wonder at finding her well-briefed . . . this president is treated by both the press and foreign leaders as if he were a child."

So why have the wolves who dined almost daily on Jimmy Carter's flips and flops suddenly fallen into a dog- like domesticity?

It is not that the press corps is unaware of the problem. Many of them feel used. Lou Cannon of The Washington Post admits the president is getting a fairer press than he deserves, but adds: "I care about him. I don't ever want to take a cheap shot at him.''

Curtis Wilkie, a maverick from The Boston Globe, is less generous. "The operative word is 'ignorant'," he says. "He's lazy. He's not stupid. He's shrewd. He's a smart politician."

Wilkie wrote that the president is like a student who can memorize a poem one day and forget it the next. A man who dislikes reading and takes to the office with an ease not seen in decades, Reagan prefers to sit in his presidential quarters and watch an evening of shoot-em-up television shows.

Reporters say they cannot continuously write bad stories about Reagan because the public howls that they are picking on him, nice grandfatherly soul that he is.

Other journalists admit that, in a strange reverse subjectivity brought on by the push for journalistic ethics, they feel obliged to let Reagan manipulate the stories because the journalists themselves do not agree with him politically. It is one of the perils of America's rules of "objective journalism" that reporters trounce their soulmates and treat their political enemies with kid gloves.

Pat Caddell, who was Carter's pollster, says it has to do with "stylistics" -- the president's performance. It also has to do with the skillful way in which Reagan's managers manipulate the press.

For example, the president has maintained he is not against women, blacks or poor people. And yet, when someone points out that his policies are hurting these groups, he can wonder out loud why all America's vast food resources should allow people to go hungry and then baldly appoint a commission to look into it.

Finally, there is the emerging media elite. Leading U.S. journalists have always been courted by politicians. Now journalists are one of the better-paid groups in Washington, and the top TV anchor jobs pay up to $2 million a year. When TV anchorman Frank Reynolds died here recently, he was given what amounted to a state funeral. The service was attended by President Reagan and he was buried in Arlington National Cemetery.

Where is all this leading? One obvious result is the emerging gap between the president as portrayed by newspapers and television and the political profile of the president pollsters are picking up.

Pollster Caddell says: "If you do a whole study of public opinion polls, the only conclusion that you could possibly come to is that Ronald Reagan is very different from the person you read about. For two years he had the lowest rating of any president since Gallup started. He is the first president to fall behind major party opposition in the Gallup poll in his second year."

Such a gap does not bode well for the American public's understanding of their candidates in 1984.