ALREADY there are people explaining that the Labour catastrophe was due to the hostility of the right-wing press. It's an interesting argument that goes to the heart of how it is that propaganda works.

For a start, there's no doubt that the overwhelming majority of the national press was hostile to Ed Miliband, sometimes breath-takingly so. Google suggests that the Daily Mail alone has published more than 4000 stories containing the phrase "Red Ed", which might have planted some seeds of an idea in quicker-witted readers. Even behind its paywall, The Sun offers a further 190 news stories containing the phrase.

While this kind of thing is worth it to the proprietors of newspapers - because it shows their favoured party leaders that they are doing their bit for victory, and so deserve favours after it has been attained - there is not much evidence that it actually sways voters.

Roy Greenslade, writing in The Guardian, came up with a convoluted conspiracy theory to explain how the right-wing press had defeated Labour. It wasn't their support of the Conservatives, but their taking UKIP seriously.

"UKIP do so well . . . because, in the five years leading up to the election, the right-wing press lent it, and its policies, credence.

"In an effort to ensure that David Cameron's Conservative party followed a largely anti-EU agenda, newspapers gave disproportionately favourable coverage to Farage and his party.

"They certainly poked fun at some of his supporters and, at various points, questioned UKIP's credibility. Yet they treated the party's policies, including its anti-immigrant stance, with undue sympathy."

This would be more convincing if there were not such overwhelming evidence that the anti-immigrant stance was overwhelmingly popular. In fact, it is hard to distinguish UKIP's policies here from those of any of the other parties. It was not UKIP that carved "Controls on Immigration" into stone, but Miliband - the tombstone that will stand over his leadership and not Farage's.

Which brings us to the central problem with newspapers as organs of propaganda. Of course they can mislead, and even lie outright. But newspapers can, on the whole, only tell people the lies they already want to believe. They generally get their effects not from the insertion of what they claim to be true, but from the rigorous exclusion of everything that does not fit into the desired picture.

When the Mail recently ran a story on the abolition of the "hated Human Rights Act", four of the six criminals whose faces illustrated it were black or brown. "Human" rights, ran the unspoken message, are foreigners' rights. The lie came not from the pictures that were used, but from all the pictures that were not.

A LOVELY example of the way the propaganda doesn't actually work surfaced in Damian Thompson's Spectator blog. A former Romanian spy, Ion Mihai Pacepa, has announced that liberation theology was actually something entirely cooked up by the KGB from beginning to end.

Not even Thompson can quite bring himself to believe that the story is actually true. "Pacepa's not into nuance, and he exaggerates. I don't believe that the KGB 'created' a movement as complex as liberation theology, and I'm far from convinced that its name was dreamt up in the Lubyanka."

He even allows that some liberation-theology priests "worked heroically among the poor".

But the whole thing is too much fun for him to abandon entirely. His conclusion is a masterpiece of weaselling: "Pacepa's interview deserves impartial critical scrutiny. But I can't see that happening, because it raises questions that are terribly embarrassing for Catholic liberals."

Impartial scrutiny, even when it is as partial as Thompson's, takes about 15 seconds to realise that Pacepa's factual claims are nonsense. The KGB did not invent liberation theology. That is the sort of propaganda that only deranged American conspiracists and KGB bosses could fall for, since they are the only people who want, for their different reasons, to suppose that the KGB was a superhumanly powerful organisation. It is not Catholic liberals who are embarrassed by this drivel, but the kind of progressives who believe in the power of human reason.

I DON'T want to suggest that it is only the Right that can persuade itself of anything. The final text for this week's sermon comes from George Galloway, the former MP for Bradford West, who lost his seat to Naz Shah, a Muslim woman who had campaigned for a boycott of Israeli firms during the Gaza War. Galloway, none the less, blamed his defeat on "the venal, and the vile, the racists and the Zionists". He still has followers.

I'm afraid that people who believe the "Zionists" run the world are a greater threat than those who suppose the KGB still does.