Since Australian Rupert Murdoch agreed to buy the failing New York Post one Chicago Saturday, he's made it the most talked-about newspaper in the city.

Most of the talk and most of the articles about the Murdoch Post have been critical, accusing the paper of everything from political bias in favor of a mayoral candidate to sensationalism over the Son of Sam killer.

Murdoch's reaction to charges of sensationalism is to wallow in it. While critics raged, Murdoch had the Post announce of its Aug. 11 edition headlining the capture of the Son of Sam suspect, "Kids who usually buy comic books bought the Post and tourists snapped back up souvenir copies to take back home."

Murdoch has never been secretive about his formula for reviving newspaper, nor has he lacked confidence in his methods.

"We're here to give the public what it wants," Murdoch says in speech after speech. (He declined to be interviewed for the article.)

he is critical of most of his fellow publishers in this country for, as he sees it, forcing unwanted news, information and analysis upon their readers. "Too often the tedium is the message." Murdoch told a publishers' meeting in San Francisco.

It didn't take Murdoch many months to make the Post controversial, but it is taking longer to make it profitable, and the Post's bottom line will determine whether Murdoch's formula inspires widespread imitation.

The Post circulation was slightly under 500,000 daily when Murdoch bought if for about $30 million. It was losing something over $500,000 a year, according to published figures.

The circulation is now 644,000, but much of the gain has been achieved in Queens, where home-delived subscriptions can still be had at half-price as part of a promotion aimed at expanding Post sales in a section of the city where it had never done well.

When The Long Island Press failed March 25, Murdoch bought up its circulation list and, according to reliable sources, had kept more than 100,000 of the 180,000 subsscribers the Press had, almost all of them in Queens.

However, newspapers generally lose rather than make money on circulation sales, particularly at half price, and the Post will not be able to turn the corner unless it can increase its advertising.

"The only problem now is setting more advertising," Murdoch said in a More magazine review.

Traditionally, according to advertising experts, large advertisers have not bought space in the Post because it is largely bought at newstands by lower-income people who are not the audience the large department stores are seeking.

As a special inducement, Murdoch began offering a free headline on the Bottom of the Post front page refering to any advertising block of eight or more pages inside the paper. The device has been used only a handful of times.

Early this year, The Financial Times of London remarked that "Many observers feel (Murdoch) will find it difficult to become a powerful political influence in New York's affairs . . ."

But on election night this month, Murdoch spent the evening with the mayoral victor, Edward Koch. A few days later, Koch paid the publisher a visit at his office.

Murdoch had backed a winner, and he had backed him to the hilt. The Post ran a series of front-page editorials supporting Koch during the campaign, concluding with a fervent election-eve plea headlined "Tomorrow: A Day of Opportunity for New York."

Fifty of the about 60 reporters working for the Post signed a petition expressing concern over what they called slanted campaign coverage.

Murdoch responded that any reporter who accuses the publisher of bias can quit. About a dozen have.

Steve Dundelavy, an Australian reporter who has worked for several Murdoch publications and has become the Post's star writer of sensational stories, sped editorial staff morale problems along when he appeared on a local television show and attacked his colleagues as lazy.

Criticism of the Murdoch methods have come from all directions outside the paper as well.

Affter the Post front page labeled New York's July blackout "24 hours of terror," Deputy Mayor Osborn Elliott accused Murdoch of seeking to build Post sales irresponsibly.

The Post, in turn, called Elliott's protest "ill considered and ill-tempered."

The Son of Sam case was the showcase this summer for what the Murdoch methods can do. Dunleavy wrote a front-page letter to the killer asking him to surrender to the Post. Some 5-year-old letters by the suspect were published under the headline "how I Became a Mass Killer," and the Post reporter in great detail how relatives of the killer's victims felt when the suspect was arrested.

"We've got no apologies to make about that coverage," Murdoch said. He directed most of it himself.

Murdoch sometimes uses the Post to act on the old Kennedy family advice: "Don't get mad, get even."

When columnist Pete Hamill criticized him. Murdoch dug out an unpublished 1971 Hamill column attacking Jacqueline Kennedy for marrying Aristotle Onassis. Hamill now dates Mrs. Onassis.

To be a New York success, however, Murdoch will have to get even on the Post's balance sheet.