Trotsky versus Hugo Oehler
Louis Proyect: "For example, the Trotskyist movement in Spain was being bombarded continuously with recommendations on what to do, but were just too small to carry them out. The POUM, on the other hand, a home-grown socialist group, did have massive influence and numbers. They made opportunist mistakes, but had much more chance of influencing events than the handful of Trotskyists."
An interesting footnote is this: Hugo Oehler has gone down in history as the ultimate sectarian but one* spawned by Trotskyism, having split over the French Turn in the U.S. Oehler held that the Trotskyists never should have entered the Socialist Party, but having entered, should have remained inside instead of leaving a year later. That difference, which Oehler regarded as one of principle, not tactics (i.e., that a decision to function within the larger mass workers' movement had to be accorded political legitimacy and commitment, not simply the aim of recruiting to the vanguard), was a central tenet of his Revolutionary Workers Party.
Yet when Oehler went to Spain, he reported that only the POUM merited support, and that the so-called Bolshevik-Leninists of Spain, beloved to Trotsky and Felix Morrow, were nowhere to be found engaged in battle. So the legendary sectarian proved less so than than the Old Man himself, while Morrow's book Revolution and Counterrevolution in Spain has remained ever since the true sectarian's scripture. To Oehler, of course, this debate was another expression of the very issue on which he had split.
(The last well-known Oehlerite was Sidney Lens, the Chicago labor leader and historian.)
*the one being Stamm, who split from Oehler, his party also calling itself the RWP, basing his distinct line on -- what else? -- the Russian question (namely, the exact year that Soviet socialism degenerated).