The pope travels to Poland and draws huge crowds. He confers with Latin-American bishops in Mexico. He appeals for social justice in his speeches. He greets his audiences in the massive Piazza di San Pietro. He holds press conferences. He's a head-strong pontiff who shakes up business-as-usual at the Vatican - not least of all because he's the first non-Italian pope in centuries. Pope Francesco I hails from the U.S.A.

Pope Francesco?

"I've joked that somebody slipped John Paul II a copy of the galleys," says Walter Murphy, whose first novel, "The Vicar of Christ," has bounced around national best-seller lists for the past few months after bouncing around Murphy's desk for more than 12 years. Murphys Pope Francesco was shattering papal precedents long before journalists began their frantic search for Polish spelling guides.

Cast in the form of interviews given to Pope Francesco's biographer by four men who figured in his life, "The Vicar Walsh, a vigorous ex-Marine who climbs to Chief Justice of the United States before suddenly resigning to become a Trappist monk. A papal conclave, deadlocked after the unexpectedly brief reigns of Paul VI'S successors, shocks the world by tapping Walsh.

Originally, Murphy had Walsh directly succeeding Paul VI'S second successor. When John Paul I died suddenly, Murphy took it upon himself to make a change in the galleys to disassociate Walsh from John Paul II.The resemblances in policy, however, # do not surprise him.

"I asked the kind of question a political scientist would ask: "What would a pope do if he wanted to maximize his impact on the world?"

Murphy has been exploring Walsh's territory for years. A former Marine combat officer in Korea, he is McCormick Professor of Jurisprudence at Princeton, a position once held by Woodrow Wilson. After nine scholarly books on the American judicial system, Murphy knows his way around legal circles, and Rome has long been a second home for him. Murphy wrote most of his novel there in a Travestere apartment.

Chatting over lunch at the American Cafe in Georgetown, Murphy pushes his choppy brown hair off his forehead. He looks the natty political science professor trying to slave off traces of literary rumple.

Later, at the circulation desk of Georgetown University's Lauinger Library, Murphy's dark suit and bulging briefcase command faculty treatment - the librarian readily offers him a conference room to talk about his book's success as both ficton and prophecy.

Originally, Murphy set out to write a scholarly book about the Vatican. He researched Vatican history thoroughly and soaked up the day-to-day atmosphere of the place during an extended residence in Rome. Although the scholarly book became a best-selling novel, some reviewers have praised "The Vicar of Christ" as perhaps the most insightful and incisive work on the modern Vatican that any writer has recently produced.

In fact, as the parallels continue to mount between Pope John Paul II and Pope Francesco - John Paul will now be following his fictional predecessor to the U.S.A. this fall - people in and out of publishing are beginning to wonder how many legions Murphy had at the Vatican. The answer, it appears is quite a few.

"I started from the most obvious place," explains Murphy. "I simply asked my friends in the American clergy to put me in touch with their friends. Suddenly you have a range of sources. Then the other side that disagrees with them hears about what you're up to and they contact you to give you a different perspective. Your sources multiply.

"One of the ways I was able to build up rapport," he continues, smiling conspiratorially," was by taking Curia people (papal bureaucrats) to lunch and dinner. The Vatican pays its people relatively little and the cost of living in Rome is about 125 percent of Manhattan. One of my sources in the Department of State told me: "Frankly, the only way I can stay in the Curia is that my father rents this apartment for me. I make enough money to buy my food, but that's all."

Murphy relates that the art of the leak flourishes at the Vatican.

"I can think of the way one Vatican spokesman who liked the Vatican policy on Israel - which was essentially one of hostility - managed to leak some comments about Golda Meir's visit to Pope Paul VI when it looked as if the Vatican might warm up toward Israel. That infuriated Golda. He nipped that little policy in the bud."

Murphy has his criticisms of the Curia, the Vatican's governing body, but years of studying it have turned him into a sympathetic admirer.

"I found very little evidence of scandal in the usual sense. I don't mean that I found a collection of saints. I can point very quickly to a couple of homosexuals, a couple of alcoholics and a womanizer. But in a population that large, if you couldn't find the percentage I found, it means you're no damn good as an investigator."

"They are people," he says, summing up the workers in the Curia, "who are very ambitious for themselves, as well as for the church."

A few months ago, Murphy was telling interviewers that his decision to write a novel rather than a scholarly book on the Vatican stemmed from a desire to protect his sources. "It's not hard," Murphy asserts, "once one knows the system, to figure out that you must have spoken to Monsignor X or Cardinal Y or Archbishop Z." Now, however, he labels that concern a "rationalization" insofar as it served as a motive for writing the novel.

"I was fooling myself," he says. "There had been this desire for awhile. I had forgotten that when I came out of the Korean war I had written a series of short stories about it - some on the backs of envelopes."

He sent those them with an encouraging letter. Murphy put his fiction-writing career back on the shelf to concentrate on graduate school. The writing itch reappeared five years later, but by then he says: "I was too much involved with all the things a young assistant professor has to get involved with - like scholarly books and articles."

Only in 1965, when tenure-track struggles could no longer spoil the charming atmosphere of Rome, did Murphy get moving on what turned out to be a whopping 632-page debut. Twelve years later, at the behest of a lawyer friend, he finally hauled the manuscript to a literary lunch with Robert Lantz, a leading New York agent. Lantz fidgeted.

"I saw Lantz look at my lawyer and I could just read the expression in his face: 'Sidney, why didn't you leave this man in his library and let me alone. I've got enough problems as it is."

"I had to laugh," says Murphy, "when he called me several months later. He said to me, in utter amazement, 'I like it,""

Lantz helped him excommunicate a few marginal characters, but left the core of the story alone, including Declan Walsh's unusual curriculum vitae. Murphy shrugs at the suggestion that Declan Walsh's ascent to the papacy strains belief.

"Of course it's implausible," he says, "but it's implausible that anybody would be pope."

With that Murphy points out that the pool of potential popes is larger than most people think. "There is no rule," he remarks, "that the Pope has to be single, or, for that matter, a priest."

Because the pope serves also as the bishop of Rome, and only a male Catholic can do so, all others are indirectly eliminated from consideration, but Murphy relates that some Church historians believe a woman has already sat on the throne of St. Peter.

"In the later Middle Ages, the newly elected pontiff, before he was proclaimed pope, was asked to sit on a chair that looked something like a toilet seat. The junior cardinal would go up under there and make sure that il Papa was a male. That's not a very attractive ceremony, but I assume it was not there just on the odd chance that you would have a woman. There must have been an offense."

As a Roman Catholic first-novelist with a professional interest in high judicial wrangling, ex-Marine Murphy seems to have wrapped some of his own biographical details in wish fulfillment when he created Declan Walsh.

"Well," he responds, "I didn't think of myself as Declan Walsh, I didn't identify with him. Robably every Roman male has fantasized at some time: "If I were pope, I'd clean out this nest." But I've never thought of it in any serious way."

Neither, he claims, should the Supreme Court portion of the book be read as a frustrated jurist's indulgence in fantasy. When he decided as a young man not to go to law school, he says, he knew that he was forsaking a judicial career.

"To be honest," he adds, "probably 75 to 90 percent of what Supreme Court justices have to do would bore me to tears, just as it bores them to tears. It has to be done, but going through the 4,000-plus petitions a year could turn one into a screaming idiot."

All the same, Murphy's reading matter lost some spice when he turned from researching the Vatican to investigating the Supreme Court - card catalogues replaced Roman menus as he relied heavily on the private papers of past justices. Despite that reliance, he cautions against reading the thumbnail sketches of the justices as an independent roman a clef.

"The only person in that section who is modeled after a real person," he maintains, "is the narrator. To some extent that's Felix Frankfurter."

He counts several members of the Court as friends. "I suspect that at least one or two of them will get around to reading it," he says hopefully. $ $&(WORD ILLEGIBLE $&)Murphy devotes much of his time right now to caring for his wife who is recovering from a stroke suffered while traveling with Murphy on a promotional tour. He's planning a biography of St. Peter and still hopes to complete his second work of fiction, a spy novel set in his old apartment in Rome.

"I think most social scientists are frustrated novelists. John Kenneth Galbraith once wrote that he turned to writing popular books after his first learned treatises sold only a few thousand copies. He said that's fine if you want to live in a closet, but if you want more people to hear what you're saying, you have to find a different medium."

Through Declan Walsh, Murphy has found the medium to talk about the politics of war, judicial intrigue, the world role of the church and of other issues. But on the subject of the ambitious, hard-nosed Walsh himself, Murphy turns out to be a tough grader.

"Most of us have a kind of internal gyroscope that tells us about right and wrong, but most of us also have a slight fudge factor. One of his problems is that he has no fudge factor I'm not sure I would have liked him. $0u:15u000u022: CAPTION: Picture, Walter Murphy, by Harry Haltchayan - The Washington Post