Anthony Howard, then editor of the left-wing <i>New Statesman</i>, once pointed out that if Huey Long had only used left-wing phraseology he would ha… - Robert Conquest

As is now generally admitted, a Soviet bomb would not have been achieved for several years more but for the success of Soviet espionage in obtaining secret information from Western scientists associated with the Manhattan Project. That is to say, political ideas in the minds of certain capable physicists and others took the form of believing that to provide Stalin with the bomb was a
contribution to world progress. They were wrong. And their decisions show, once again, that minds of high quality in other respects are not immune to political or ideological delirium....In the Soviet case, those involved thought they knew better than mere politicians like Churchill. They didn't.

On political matters basically the best, though not infallible, source is rumour at a high political or police level.

There was an old bastard named Lenin
Who did two or three million men in.
That's a lot to have done in
But where he did one in
That old bastard Stalin did ten in.