As for any collusion in the 1953 Candidates Tournament, I found the following in Chess Review, November 1953 (p.323):
[Reshevsky] entered the tournament not at all certain that the nine man Russian "syndicate" would be overly concerned with "bourgeois" standards of sportsmanship. At Saltsjobaden there had been undeniable collusion by the Russians in a move to freeze out Western competitors. Might not the same tactics be repeated at some critical stage in the present struggle if it became expedient to throw collective support to the Soviet candidate whose prospects had crystallized above those of his fellow Russians? Regarding this possibility, the Australian Chess World remarked in a pre-tournament issue that "we fear the Russians would put patriotism above the canons of sport, as at Saltsjobaden, and make things a bit easier for the top Russian."
While Chess Review has no evidence that such collusion was either planned or practiced in Switzerland, the ever-present threat operated as a mental hazard that could not but adversely affect the play of the Western group. An indication of the peculiar Russian mentality on this point is seen in the intransigent attitude of Ragozin, official spokesman for the Russian delegation, during an interview with the American journalist and master, George Koltanowski. When George started to ask a question beginning, "If a non-Russian were to win this tournament..." Ragozin brusquely interrupted: "Nyet! Never! Impossible!"
Why players of the calibre of Reshevsky, Najdorf, Gligoric and so forth should be ruled out summarily is difficult to see, even if we grant the undoubted capabilities of the Russian stars. Was Ragozin merely voicing a personal opinion as to the probable outcome? Or was he expounding an official a priori dogma that no non-Communist will ever be alowed to win a challengers' tournament if the Russians, by hook or by crook, can possibly prevent it?
Another ugly (and rather astonishing) blot on the tourney, according to information received from one of Chess Review's observers on the scene was the unabashed consultation by the Russian contingent -- "flagrant coaching from the sidelines ... and tips passed from one Russian player to another during games".
Despite the lack of 'evidence that such collusion was either planned or practiced', the threat was as strong as the execution, at least for the editors of Chess Review. The article went on to mention that Reshevsky played the event without a second, which certainly didn't improve his chances of succeeding.