John B. Anderson met his maker during the last week, and the result of the meeting evoked those old St. Peter jokes in which the supplicant fails some test and is exiled to the lower depths.

This is decidedly not a religious story. Anderson's maker is the same secular force that made Jimmy Carter and Ronald Reagan -- America's mass media. The media, with some crucial help from the public opinion polls, first designated Anderson a potentially serious challenger. This past week, the media -- again with invaluable assistance from a national poll -- revised and extended their remarks.

Anderson was stunned and debilitated by a flurry of negative publicity that began last Friday. This timing suggests that Anderson's fate was resolved on schedule -- or at least suited some never-published timetable against which political analysts in the media have been clocking Anderson's candidacy from the outset.

A week ago Sunday Anderson had his one bright shining moment. For months his handlers had said he had to be invited to the League of Women Voters' debate, and he was, and he debated -- against only Ronald Reagan, to be sure, but the Anderson camp hoped this debate could light a match under the independent's campaign.

A panel of debating coaches judged Anderson the winner over Reagan on points, but rarely. Ordinary viewers probably saw a draw, or a victory by whomever they already, supported. But within days, the media's purveyors of conventional wisdom saw the functional equivalent of a defeat.

This was not defeat in the football game sense. Anderson did fine in the debate, but he didn't do anything to solve his basic dilemma. He went in a marginal longshot, and after a journeyman's performance he came out a marginal longshot. So he failed to exploit his best opportunity of the campaign.

Conventional wisdom in politics resembles any small structure made of bricks. Just a few bricks can create a formidable edifice, provided they materialize in a timely fashion. In this case, the first brick came from Jack Germond and Jules Witcover of The Washington Star.

Last Friday, in an exclusive frontpage report, the paper's political columnists wrote:

"With some exceptions, Anderson's leading supporters and advisers have abandoned their dream of winning the election . . . This does not suggest that Anderson's backers are throwing in their cards, but only that they now see the rest of the campaign as a case of playing out their hands against essentially hopeless odds."

This was a carefully written article. Germond and Witcover -- popular and respected political journalists, known personally to all the print and TV reporters covering this election -- took care not to write Anderson off. tWith luck and an infusion of money he might still win Massachusetts and Connecticut, they wrote; "at a minimum" he might "hold the balance of power in several larger states such as New York and Pennsylvania and possibly California."

Of course, Germond and Witcover -- like all the other major political commentators -- had avoided declaring at any earlier stage that Anderson was a potential winner. The conventional wisdom has long been a variation on the old children's story: We think he can't, we think he can't, we think he can't -- and now, he can't.

On Saturday The New York Times virtually duplicated the Germond-Witcover report, with additional details to justify the assessment that "the independent candidate no longer has a serious chance of winning the election." Warren Weaver Jr., an experienced political reporter who has been covering Anderson for months, attributed this view to "the key strategists" in the Anderson campaign.

Like Germond and Witcover, Weaver wrote that some of Anderson's advisers blamed the candidate himself for being too inflexible and not grasping the opportunities of his independent campaign, while others blamed Anderson's demise on bad luck and the failure to raise more money.

These two bricks put a good foundation under the new conventional wisdom. Saturday night, CBS and NBC contributed a superstructure with pessimistic news pieces on Anderson. Said Bob Faw on CBS: "The Anderson campaign is trying harder and still sputtering. The political breakthrough aides hoped would follow the debate hasn't happened." Jim Cummins of NBC said, "By midweek, Anderson was feeling left out." (He was indeed all but completely left out of the networks' evening news shows on Tuesday, Wednesday, Thursday, and Friday.)

Saturday night and Sunday morning brought the first poll results that tended to confirm the new, gloomy line. The CBS/New York Times poll had divided its usual national sample of about 1,600 potential voters, questioning 800 of them before the Reagan-Anderson debate and 800 afterward. The results were devastating for Anderson.

CBS emphasized the bad news for Anderson in the poll, but the Times account did not. Nevertheless, the Times printed the key numbers -- Anderson's overall support had declined to 9 percent, and voters who watched the debate and developed stronger negative feelings about him.

Also on Sunday, the dean of political journalists, David S. Broder of this newspaper, added a brick to the new edifice. Broder's Sunday column reported on an unsuccessful Anderson visit to Philadelphia last week. The visit was "a vivid demonstration of the limits of media politics," Broder wrote, a "fiasco" that tended to confirm predictions from the Reagan and Carter camps that Anderson was going nowhere.

So a new conventional wisdom is now in place. It does say Anderson can still be "a factor" Nov. 4, but this ritualistic hedge could soon disappear. The new line on Anderson could prove infectious; if it does, the candidate's biggest problem -- no money -- will only get worse. No banks have yet announced a willingness to lend him money, and the bankers won't become more generous if the prognoses get more gloomy.

To fight the gloom, Anderson's senior aides collaborated on a long letter to the editor of The Washington Star, published yesterday, "emphatically" denying the import of Friday's GermondWitcover article. Included in this effort at group optimism was the following assertion:

". . . The more people learn about John Anderson, the better they like him. The New York Times/CBS poll of Sept. 17 showed a steady rise in favorable impressions of Mr. Anderson . . ."

Anderson's aides apparently decided to ignore the Sept. 28 CBS/Times poll, which showed just the opposite. Even before the debate, Anderson's favorable rating among voters had registered "a huge drop," according to Warren Mitofsky of CBS, who administers the poll.

Worse for Anderson, voters questioned after the debate gave him a much higher unfavorable rating than those who were polled before it took place. Voters split 19 percent favorabe, 24 percent unfavorable in their pre-debate impressions of Anderson, and 20 percent favorable, 31 percent unfavorable afterward.