While browsing the excellent site, Chess Café, I came across an interview with Soviet GM Yuri Averbakh conducted in 2002. In Part 1 he touched on the rumor that Paul Keres had been forced to avoid challenging Botvinnik for the world championship. Since Keres lost his first four games against Botvinnik in the 1948 World Championship tournament, suspicions were raised that Keres was forced to throw games to allow Botvinnik to win the Championship. It was said Soviet chess officials gave Keres strong hints that he should not hinder Botvinnik's attempt to win the World Championship and Botvinnik discovered this about half-way through the tournamen. Botvinnikt said when he discovered this he protested so strongly that he angered Soviet officials. Most people believe Keres probably did not deliberately lose games to Botvinnik or anyone else in the tournament. Samuel Reshevsky once said he did not think Keres could have ever won the world championship because his play was too unsteady. Interesting reading.