Rupert Cornwell: The voices of America who ruled the world

Out of America: A new play recalls the huge political influence writers once had

John Lithgow portrays legendary columnist Joseph Alsop in a new Broadway play (AP)

Theses days, even American political buffs may have forgotten who Joseph Alsop was. If so, a visit is in order to David Auburn's fine new play The Columnist, which opened on Broadway last week. The first scene is startling enough, featuring Alsop, the ultimate Cold War warrior, in a hotel room in Moscow in the 1950s, where he has just had sex with a young Russian man – the whole episode filmed by the KGB. But what the play really brings home is the extraordinary influence once wielded by a tiny group of Washington newspaper columnists.

In Britain, it's always been newspaper proprietors, rather than those who scribble for them, who matter. But in America, over a substantial period in the middle of the 20th century, columnists ruled. They included James Reston, Drew Pearson and Walter Lippmann. But no pen was mightier than the one belonging to Joe Alsop.

Alsop was a fascinating character. He was a Harvard-educated East Coast patrician, whose mother was the niece of Teddy Roosevelt. But instead of going into industry, Wall Street or government, he became a reporter. He was brilliant and conceited yet oddly insecure, a complex and difficult man who spent his life burdened by the secret of his sexuality which, if exposed, might have destroyed him.

His great professional fortune was that the peak of his career coincided with the golden age of Washington columnists, roughly between the Second World War and 1970. The US had emerged from the conflict the most powerful country on earth. Yet television was in its infancy, and the capital still a small, clubby town where much policy was thrashed out over Georgetown dinner tables. With their thoughts syndicated in hundreds of papers across the country, the top columnists had the opinion-shaping field to themselves.

Republican administrations were less susceptible to their charms – Eisenhower claimed never to read them, while Nixon stuck the ones he didn't like on an enemies list. Under Democrats, though, they thrived. Kennedy not only understood the press, he liked it, and Lyndon Johnson would do anything to have it on his side.

Nor was the KGB the only group in the Soviet Union to grasp the columnists' influence. Back in 1958, Nikita Khrushchev invited Lippmann and his wife to a hunting lodge in the Urals to discuss how to thaw out the Cold War (a term, incidentally, coined by Lippmann). Two years later Kennedy won the presidency, ushering in the golden age of Joe Alsop.

By upbringing, Alsop was a Republican, but he had long been a supporter and friend of Kennedy. In those days, Washington politics were nothing like as polarised as now. Kennedy privately consulted with Alsop at the 1960 convention about his choice of running mate; and, on inauguration night, repaired to Alsop's house in Georgetown, where the two talked until almost dawn. The topics may have included the myth of the "missile gap" between the US and the Soviet Union, propagated by Alsop's columns, which Kennedy had used to great effect against Nixon in the campaign.

Alsop's access was matched only by his self-regard. David Auburn cites a call Alsop made to Johnson, soon after he entered the White House, in which he constantly interrupts the president, "No, no, Lyndon, you don't understand..." Reston, while less close to Kennedy, owed his inside track to his position on The New York Times. Immediately after the bruising Vienna summit with Khrushchev in 1961, he was summoned for his first interview with Kennedy. In an astonishingly frank talk between president and journalist, Kennedy told Reston that the meeting had been "the worst thing in my life – he savaged me". Reston naturally didn't disclose his source. Columnists were trusted – and, many would say, too trusting.

But Reston may have sensed that the golden age could not last. Early on, he told Kennedy that the new president's plan to hold televised press conferences was "the goofiest idea since the hula hoop". In fact, it was the beginning of the end for the columnists' monopoly. Gone are the days when a few priests at the oracle of power spoke wisdom unto the masses.

Columnists still exist, and some enjoy enviable access. But their clout is gone. President-elect Obama did go through the motions in January 2009, dining with a group of conservative columnists. But much good it did him. And the one opinion-monger who might have Alsopian clout – the conservative talk-show host Rush Limbaugh – wasn't invited.

Alsop's eventual undoing was not his gay encounter in Moscow. He refused to be blackmailed by the Russians and made a report of the entire incident to the CIA. Amazingly, the scandal never went public. His sexual preferences were common knowledge but gentlemen didn't blow the whistle on such matters.

What finished Alsop was his unreasoning support for the Vietnam War. His stand was a product of his anti-communism – but in part, too, surely, of his habit of listening exclusively to those in high office. Any similarity with American punditocracy's embrace of the official rationale for invading Iraq in 2003 is coincidental. But then again, maybe the old ways haven't died after all.