EVERYONE has their favourite conspiracy theory. Correction — every man has his favourite conspiracy theory. You can take your pick. Harold Wilson was a communist spy, the imprisoned Hess wasn’t the real Hess, there is a Zionist plot to control the media, the world is being run by giant lizards who can transform themselves at will into Henry Kissinger. I didn’t make any of these up, either. There are people who really believe them.

And then there are those who hold to the most swivel-eyed conspiracy theory of all — that there are no conspiracies. They are the ones you really have to watch out for, obsessional in their belief that all suspicious events are one giant series of unrelated cock-ups. I’m sorry, but that’s just so implausible.

Until recently my pet conspiracy was the assassination of President Kennedy. Honestly, you don’t want to get me started. I’ve read enough books on the subject to fill the sixth floor of a medium-sized school book depository.

I still don’t believe (I think) that Lee Harvey Oswald acted alone, but I have to admit that I’m beginning to go off the Kennedy conspiracy.

To start off with, it has proved a bit of a social embarrassment. The robust thing to believe, the manly thing, the thing that Kevin Costner says in Bull Durham that he believes, is that Kennedy’s assassin was a lone gunman. I’ve learnt to avoid admitting to my contrary opinion, especially as I share my position, which envisages a fairly simple conspiracy, with nutters who believe that Kennedy’s body was swapped and that a police officer looking like JFK is buried in his grave in Arlington.

Another problem with being a Kennedy conspiracy theorist is that it’s all so much work. The literature on the Dallas murder is now so vast that it is possible to count yourself an expert only if you specialise. There are autopsy specialists, acoustic evidence specialists, false Oswalds specialists, bullet specialists and so on. Life’s too short.

The final difficulty is that, interesting though the speculation might be, it’s hard to believe that it really matters. Kennedy’s death mattered, of course, and it would have mattered a great deal if it had been seen as a conspiracy at the beginning, but by now it’s all just a rather ghoulish episode of Inspector Morse.

So I’ve decide to change favourite conspiracies (you’re allowed to do that — it’s not like a football team). I’m going to start reading sceptical books about the Kennedy conspiracy and leave the grassy knoll to head back to my first love — Watergate. It was reading about Watergate that first hooked me on politics and this week, with the 30th anniversary of President Nixon’s resignation, it still looks pretty alluring.

Watergate has the advantage that its status as a genuine conspiracy is undeniable. And fans of “the cock-up theory of life” might wish to note that it was a pretty bizarre, complicated conspiracy at that. When the investigative reporter Carl Bernstein was first assigned to the story that made a name for him and Bob Woodward, his friends found completely ridiculous his conviction that the trail from what appeared to be a simple break-in stretched all the way to the White House.

A more significant advantage still is that Watergate is unquestionably extremely important and therefore worthy of any attention I might lavish upon it. Indeed, I would argue that the scandal is among the top five most significant political events of the postwar era. It did more than anything else to change the relationship between politicians and the media.

Has this been entirely beneficial? That’s a more difficult question.

At first I think the answer was unequivocably yes. In America politics was horrendously corrupt. Both of Nixon’s predecessors, Kennedy and Johnson, were strongly linked to electoral fraud, backhanders were routine and the Mob was ever present. Much of this behaviour was overlooked by a quiescent media. British politics has never been like this, but the deferential attitude of journalists nevertheless meant that much that should have been questioned went unquestioned.

Watergate changed all this. Journalists became more assertive, suspicious, and, of course, ambitious to find the next Watergate (or something to which the suffix “gate” could be appended). The results included cleaner politics and greater accountability. These were straightforward gains.

Now, however, I think things are changing. There will never be a return to the pre-Watergate habits but an insidious transformation is taking place. Valuable suspicious alertness is hardening into cynicism. The desperate desire among journalists to be the next Woodward and Bernstein is producing more and more so-called scandals of less and less importance. The assertive journalist is beginning to swap a feeling of equality with his subject with one of contempt for his subject.

This change has an ironic result. If all public figures are believed to lie all the time, people stop caring about whether an individual statement is true or an individual action is moral. The constant search to unearth the facts becomes boring when observers are sure it is all a big con anyway.

If someone like Nixon were up to his neck in the equivalent of Watergate now, voters might easily end up shrugging their shoulders. I mean, they sort of knew that about him when they voted, didn’t they? Just like Clinton and his women. Why do those journalists go on and on?

Unless we regain our sense of proportion the benefit of that great scandal will be lost. Which in itself would be a scandal. Watergategate.

STRAW TOLL

I’ve enough difficulty persuading waiters not to fill my soft drink with 78 pieces of ice and a large slice of lemon or half a grapefruit or whatever. Now a new menace has arrived. Even in a posh restaurant they add a straw into the concoction. What’s the point? You can’t possibly sit there drinking through a straw at a business lunch. Anybody got any ideas on how to prevent this ridiculous new custom?

FAT’S THE QUESTION

The cover of this week’s Public Health News asks “The Obesity epidemic — are food councils the answer?” Er, no.

daniel.finkelstein@thetimes.co.uk