Handwritten changes to the manuscript of the novel "Primary Colors," the wildly successful satire of the 1992 Clinton campaign by an author known only as "Anonymous," appear to match the handwriting of Newsweek columnist and CBS commentator Joe Klein.

At the request of The Washington Post, Maureen Casey Owens, a top document examiner and past president of the American Academy of Forensic Sciences, studied Klein's own handwriting alongside copies of amended manuscript pages. She concluded that "the two samples of handwriting are absolutely consistent throughout."

In the past, Klein had vehemently denied being the author of "Primary Colors." "For God's sake, definitely, I didn't write it," he said in February, and even told a Washington Post editor he would stake his credibility as a journalist on it.

He didn't deny it yesterday, however. Confronted by telephone with the handwriting analysis, a vacationing Klein at first asked for five minutes' grace, then called back to say, "I have no comment." Asked if he wrote the novel, he ended the phone call by saying, "I've said everything I have to say."

The quest for the author riveted political circles last winter, especially after President Clinton teased the press corps by saying it was "the only secret I've seen kept in Washington in three years." More than 1.1 million copies of the novel are in print in this country alone. A big-budget Hollywood movie is in development.

The mystery began to unravel with the help, first, of a secondhand bookseller, who offered for sale a bound manuscript of "Primary Colors" dated April 1995 -- just after Random House acquired it. Marked "CONFIDENTIAL! For your eyes only!! Do not distribute to booksellers!!," the typescript boasts brief snatches of handwriting on several pages.

From another source, The Post obtained several pages of Joe Klein's own handwriting.

To the untrained eye, the two handwriting samples looked remarkably similar. But perhaps this was merely wishful thinking. So The Post hired Owens, for many years the chief document examiner for the Chicago Police Crime Laboratory, who frequently testifies about handwriting comparisons in court. She cautioned that although there were many matches, it would have been helpful if the manuscript had had more handwriting, and that she would have liked to have examined the original manuscript, rather than a second-generation photocopy.

Still, she said, "there is nothing I see that is divergent. Everything is in agreement." While handwriting analysis is not as scientific as, say, fingerprinting, Owens noted that "we've never found two people who write exactly the same. Even twins."

Kathy Robbins, the agent for both Anonymous and Joe Klein, declined to comment yesterday. The book's editor, Daniel Menaker, and Random House Publisher Harold Evans both suggested that they may have written the notes on the manuscript. However, neither would provide a sample of his own penmanship for comparison.

"Let's leave the mystery open," Evans said. "You go and do the story. It's fine by me." The publisher has always said he did not know the identity of the author.

Klein was mentioned as a suspect in the very first story about "Primary Colors," more than a year ago. Then -- partly because the novel contains an unflattering portrait of a reporter who resembles Klein -- the case for his candidacy flagged. When suspects were being discussed on Larry King's TV show, he wasn't mentioned. The Washington Post put the odds on Klein's authorship as 50 to 1 -- much worse than it gave for "Doonesbury" cartoonist Garry Trudeau, campaign consultant Mandy Grunwald, White House aide George Stephanopoulos or novelist Christopher Buckley.

Still, there were believers in Klein. The first to make a good case was former Clinton speech writer David Kusnet, writing in the Baltimore Sun. He pointed out that both Klein and Anonymous have a deep interest in New York City politics, and that they had the same attitudes on race. Klein himself admitted that Anonymous was obviously "a very close reader of my column and probably watched me on TV a lot, and may even have been someone I've spoken to."

Kusnet's piece was followed by a much more heavily publicized article in New York magazine. Donald Foster, the Vassar professor who had used computer analysis to convince scholars that Shakespeare was the author of an obscure elegy, was hired by New York to do the job on Anonymous. After winnowing through a bunch of suspects, he came up with Klein, and demonstrated at length how they both loved adjectives with "y" endings, such as "talky," "slushy" and "sleazy," among other comparisons.

The article stated unequivocally that "Joe Klein wrote Primary Colors,' " but it quickly turned out that Foster didn't write that -- New York Editor Kurt Andersen did. "I think it's quite possible there are two people involved in the book," Foster waffled. Klein, who wasn't quoted in the article, put a lengthy message on his voice mail denying all.

Published in late January, "Primary Colors" had a first printing of 62,000 copies, a good but not great number for a commercial novel. Random House, as the cover of the April 1995 manuscript reveals, always intended to milk the whodunit angle. The cover announces a "publicity campaign to tie in with presidential primaries -- copies to press covering the candidates, political columnists and opinion-makers, and a guess-who campaign pitched to national TV, radio and print."

The magical thing was, they didn't even have to work for it. Inspired by good-but-not-great reviews and the guessing game, interest in the book immediately developed into a frenzy that astonished even hardened publishing veterans. With royalties along with paperback, movie and foreign rights, the book will earn its author at least $6 million, and probably considerably more.

Although the book is now off the bestseller list, sales remain brisk. Random House is still running frequent ads, and has been planning to distribute buttons proclaiming "I Wrote Primary Colors' " at both political conventions. And the publisher has submitted the novel for a Pulitzer Prize, which required agent Kathy Robbins to write a letter attesting that Anonymous was a U.S. citizen.

Klein has been living well, if not exactly lavishly, in the past year. In July 1995, a few months after Random House bought "Primary Colors," he bought a $630,000 house in Pelham, a New York suburb, real estate records show.

He took on a $310,000 mortgage, suggesting that he plunked down $320,000 in cash. Three cars are registered in his name in New York -- an Acura and two Fords. The newest is two years old. The gossip at Pelham dinner parties this spring was that Klein's daughter was boasting at school, "My daddy is rich."

"Primary Colors" editor Menaker said yesterday that Anonymous should be left alone. "The attempts to pursue the author confirm some of the book's ideas about the tendency of our media to let no stone go unturned, even a stone that doesn't want to be turned," he said.

But the issue has been kept alive by the author himself. On May 19, just as the speculation was dying down, Anonymous wrote a lengthy essay for the New York Times Book Review that caused it to flare all over again.

He complained about the frenzy ("it's . . . been pretty perverse and occasionally nauseating"), waxed coy ("My spouse nuzzled my ear one evening and asked, Can I, y'know, do it with . . . Anonymous tonight?' ") and promised to write again. WHO WROTE "PRIMARY COLORS"? Handwritten changes in the manuscript of the book (below left) appear to match the handwriting (below right) of Newsweek political columnist Joe Klein. A leading forensic analyst calls the two samples "absolutely consistent." Klein, who in the past has denied writing the book, refused to comment when informed of the new evidence, some of which is shown here. CAPTION: An "on"-the-nose match: A comparison of handwriting from the manuscript of "Primary Colors" and Newsweek columnist Joe Klein.