Theodore H. White, 71, one of the most influential journalists of the century and the author of "The Making of the President -- 1960," a classic study of politics that changed the way candidates plan campaigns and reporters cover them and ultimately, therefore, the way citizens choose their leaders, died May 15 at Lenox Hill Hospital in New York City. He was hospitalized May 9 after a stroke.

In addition to five volumes on presidential elections, Mr. White wrote two novels and books on the Far East and Europe, where he had a distinguished career as a foreign correspondent. He also wrote "Breach of Faith: The Fall of Richard Nixon."

In a statement issued by the White House, President Reagan said Mr. White was "truly an American institution . . . a familiar part of the American political fabric -- observing and explaining the very essence of our democracy.

"In books which have become works of historical importance, Teddy White taught us much of ourselves and our country," the president said. "Somehow a presidential campaign was not really over until Teddy's book was written.

"He was a true professional -- tough and insightful, but always fair. He respected and understood the presidency and took us behind the scenes with a special wisdom and sensitivity."

"The Making of the President -- 1960" sold more than 4.2 million copies and was awarded the 1962 Pulitzer Prize for general nonfiction. It not only told how John F. Kennedy defeated Nixon for the presidency, but also how the young Bostonian won his party's nomination and how he ran his day-to-day campaign.

This profile of the political process was told within the broad outlines of the demographics, the culture and the economics of the time, and it was illuminated with telling details, asides and anecdotes. For example, Mr. White interviewed Gaylord Nelson, then the governor of Wisconsin, and learned that the traditionally liberal midwestern state was having difficulty paying for the broad range of social programs it supported. The reason: the fastest growing segments of the population were the very young and the very old -- groups that require much in the way of services but contribute little in the way of taxes.

"The Making of the President -- 1960" became a standard textbook in colleges and universities and a bible to pollsters, pundits and politicos. Its influence spread beyond American shores. Harold Wilson, a former British prime minister, kept an underlined copy at hand and French president Charles de Gaulle gave copies to every member of his cabinet. Copies were just as eagerly sought in the emerging societies of the Third World.

Mr. White repeated his tour de force for the elections of 1964, 1968 and 1972. He skipped 1976, but his 1980 volume reviewed all the presidential campaigns from 1956 through that year. Each entailed a daunting amount of legwork -- untold thousands of miles of travel and years of research. And each appeared as an exceedingly readable account of a very complex process.

William Greider, a columnist for Rolling Stone and a former political reporter and national editor at The Washington Post, called Mr. White "the premier political reporter of our time" and said that he "writes like a fair wind, refreshing the landscape. He tells a story so well that familiar events become compelling, pulling readers forward to a climax they already know."

Following Mr. White's lead, other journalists began putting entire campaigns under a kind of magnifying glass and producing book-length reports. Included were such details as what a candidate had for breakfast, and Mr. White, who professed to be embarrassed by the trend he had started, said politicians were in danger of losing the last remnants of their privacy.

Mr. White was not without critics. Some wrote that he appeared to be in thrall to winning candidates, especially Kennedy. Others said his books attempted to be morality plays in which the election process consistently produced things of beauty. Others asserted that campaigns were becoming so long and complex that they could not be covered by one person -- not even by Theodore H. White. Moreover, they said, if Mr. White could operate as a fly on the wall in 1960, he was a celebrity in his own right by 1964.

Like many great enterprises, "The Making of the President" series almost died aborning. An established journalist who had written several well-received books, Mr. White nonetheless had difficulty in interesting publishers in his project. But he had just sold the movie rights to his second novel, "The View From the Fortieth Floor," which he himself called "one of worst novels ever written," to Gary Cooper. It was the proceeds of this transaction that allowed him to undertake the 1960 book: he bet his own money on his idea.

Political columnist Robert Novak told Newsweek magazine that "in 1960 everyone felt sorry for Teddy White. Here was a guy spending all his money on a harebrained scheme. Who was going to buy such a book nine months after the campaign?" By 1965, Mr. White had made an estimated $500,000 from his first book and was guaranteed $100,000 for his 1964 effort.

Theodore Harold White was born in Boston on May 6, 1915. After his father died, the boy helped the family make ends meet by selling newspapers at a streetcar stop. He graduated from Boston Latin School, the rigorous academic haven for intellectually gifted children in the city public school system. Then he went to Harvard University on a newsboy's scholarship and studied history and Asian languages. He was elected to Phi Beta Kappa, and he graduated summa cum laude in 1938. Armed with a Sheldon Traveling Fellowship, he traveled to Europe and then the Orient, where he planned to perfect his languages.

His Harvard-accented Mandarin proved incomprehensible to Chinese. After mastering the colloquial language, he took a job as a Chinese government translator and contributed stories to the Boston Globe and the Manchester Guardian.

He planned to return to this country and teach Chinese until he witnessed a Japanese bombing attack on Peking in 1939. Years later Mr. White said, "They burnt it -- they burnt it -- 3,000 human beings died. Once I had seen that, I knew I wasn't going home to be a professor." And so he turned to his life's work.

John Hersey recruited him for Time magazine. When Henry Luce, the publisher, visited Asia, he and Mr. White quickly struck up a friendship. Over the years they often argued, but their regard for each other outlasted their differences. During World War II, Luce and the young chief of his China bureau disagreed about U.S. policy. Luce, the son of missionaries in China, had a great love for the country and for Generalissimo Chiang Kai-shek. Mr. White shared Luce's feelings for China, but he despised the nationalist leader.

Mr. White was told to stop filing stories on Chinese politics and confine himself to war coverage. He did so with a vengeance. He flew on so many American combat missions that Luce finally "grounded" him. But not before he was awarded a special Air Medal from the Army Air Forces. He ended the war on the deck of the battleship Missouri, where he witnessed Japan's surrender.

In 1978, Mr. White published a volume of memoirs, "In Search of History," and in it he told of allowing Chou En-lai, later premier of communist China, to persuade him, a Jew from Boston and a reporter gifted with world-class powers of observation, that a dish of pork actually was a dish of duck. He said that Chou, Gen. Joseph Stilwell and President John F. Kennedy were the only three men "in whose presence I had near total suspension of disbelief or questioning judgment."

After the war, Mr. White left Time. With Annalee Jacoby, he wrote "Thunder Out of China," which appeared in 1946 and became a best-seller. Two years later he edited "The Stilwell Papers." In 1947, he worked briefly for The New Republic. He later recalled that "six months on a liberal magazine will cure almost any illusion. The dogmas were more constricting than those at Time."

The year 1948 found him back in Europe. He was a free-lance writer and also worked on the staffs of the Overseas News Agency and The Reporter magazine. He wrote his second book, "Fire in the Ashes," about the Marshall Plan and Europe's economic recovery from war.

In 1953, he returned to this country as a national correspondent for The Reporter and wrote a novel about China, "The Mountain Road." He also worked briefly for Collier's magazine before it went out of business.

Mr. White, who lived in New York City and Bridgewater, Conn., was married first to the former Nancy Ariana Bean. Their marriage ended in divorce.

Survivors include his wife, the former Beatrice K. Hofstadter, of Bridgewater and New York City, and two children by his first marriage, Ariana Van Der Heyden and David Fairbank White, both of New York City.

Over the years Mr. White learned about many things, and he turned his information into journalism that came as close to the truth as anything can in a world of unending complexity. But his own view of his role was simplicity itself.

"My trade is the witnessing of events and writing about them as well as I can," he once said. "I'm flattered that people do call me a historian or a social analyst or anything like that, but I'm just the man who happens to be around when things happen, and I like to tell stories about them. You can call me anything you want."