I remember Sidney Blumenthal from my time in Washington in the late 1980s when I was there as the first American editor of the Independent. He was a smartly dressed, agreeable political journalist, handsome in a donnish kind of way, who had a gracious, dignified manner that seemed to put him a cut above most of his fellow hacks. He was also a liberal of strong political conviction, whose purpose was to help rebuild American liberalism so that it could take on and beat the New Right after its long ascendancy under Ronald Reagan and restore the Democrats to power. It was at around this time, in 1987, that Blumenthal first met Bill Clinton whom he came to regard — rightly, as it turned out — as the Democrats’ best hope for achieving this aim.

In 1993, at the start of Clinton’s first term as president, I went to New York to work on the New Yorker magazine, where I found Blumenthal had been hired by the new editor, Tina Brown, as chief political writer. By then he had already become close to both Bill and Hillary Clinton, and in 1997 he went to the White House as a senior presidential adviser. Before that he had written a long New Yorker profile of the new British Labour leader Tony Blair whom he saw as an ideal international partner for Clinton, whom Blair in turn sought to emulate in his quest for power. Clinton had called himself a ‘New Democrat’; Blair invented ‘New Labour’. And Blumenthal brought them together as fellow advocates of the now generally forgotten ‘Third Way’, which seemed to propose some sort of blend of the best of capitalism with the best of socialism.

Blumenthal found himself in the thick of the Monica Lewinsky scandal, stoutly defending Clinton against those seeking his impeachment, and this brought him yet closer to the President’s betrayed wife, Hillary, with whom he spent many sessions discussing strategy. He never actually had a formal job for Hillary, but he was an active adviser to her during her first run for the presidency and then remained very close to her when she re-emerged as Barack Obama’s secretary of state. As we all now know, Hillary used her personal email address for government business when she shouldn’t have, and of the latest batch of emails released by the state department in response to a court order, 306 were messages from Sidney Blumenthal.

Well, Blumenthal is a clever fellow, the author of several books, now engaged on a gigantic four-volume biography of Abraham Lincoln, but on British politics, one of his vaunted areas of expertise, his advice is not always useful or, indeed, reliable. For example, in the run-up to the 2010 British general election, he described to the secretary of state how ‘James Murdoch and his wife stormed into the offices of the Independent, not a Murdoch paper, when the paper endorsed the Liberal Democrats and confronted the publisher, screaming in the middle of the newsroom,’ whereas the ‘wife’ of James Murdoch was in fact Rebekah Brooks and the reason for their screaming had nothing to do with an endorsement of the Liberal Democrats but was in response to the paper running an advertising campaign with the slogan ‘Rupert Murdoch won’t decide this election. You will.’

Of even less value to Mrs Clinton, I would have thought, was his assessment of the personalities of the two party leaders who were to emerge from the election as prime minister and his deputy. While David Cameron was a snob, he said, Nick Clegg had an ‘inbred arrogance (from no less a privileged background than Cameron, though seeming less snobbish because he went to Westminster instead of Eton)’. Well, Cameron went to Eton — I won’t argue with that — but there is no reason to think him snobbish, unless you think, as Blumenthal apparently does, that every Old Etonian must be.

In any case, how could such tired old clichés about Britain be helpful to the American government in its dealings with British leaders? Yet Mrs Clinton responded to this information by saying she had shared Blumenthal’s emails with her husband, Bill, and that he had thought them ‘brilliant’. ‘Keep ’em coming,’ she said. Another well-worn cliché over here is that Americans are naive when it comes to understanding the rest of the world. I don’t usually agree, but this sort of thing makes one wonder.