1901, good choice. Before "What is to be Done?", basicaly the textbook for the so-called "vanguard party", and before the Bolshevik-Menshevik split, so a united RSDLP which will not be limited in membership to "full-time revolutionaries", but rather a genuine mass party. Lenin had no major role in the 1905 revolution, so presumably that goes off roughly the same. Given the only changes will be in obscure left-wing parties, we can probably assume that some kind of war occurs between the European powers in the mid 1910's, so Russia will still be subjected to the stresses and strains which led to revolution in OTL. Assuming some kind of dual power emerges like OTL, it's probably safe to assume that the presence of a unified Marxist bloc and the lack of democratic centralism will allow the fragile situation to continue much longer than OTL, possibly with an alliance between the RSDLP, the SRs and a few liberals controlling the Assembly as well as the Soviets. Sure, there will be marginal figures like Trotsky who are opposed, but without Lenin's April Theses the slogan of "All Power to the Soviets" will probably take longer to form. The real split, I think, will come over whether or not to continue the war. Perhaps the left RSDLP will merge with the left SRs in this situation, demanding an immediate end to the war, Soviet power and the division of land among the peasantry. It will be a fragile coalition to be sure, and I'm not sure it would be able to survive the horrors of civil war, but it certainly has a better chance of doing so without degenerating than the centralised, inward-looking and bureaucratic Party created by Lenin.