So I recently wrote a term paper on the Socialist Revolutionaries in Russia, and I developed a bit of an affection to the, mainly due to their endearingly schizophrenic manifesto ("We want an 8-hour work day, no child labour, land reform and workers comp! To get that, we advocate terrorism and a revolutionary dictatorship!"). So, Your challenge, should you choose to accept it, is to get the SR's in a position of essentially unchallenged power in at least modern Russia and Ukraine with a POD after Stolypin's coup. Bonus points for a POD after the beginning of WW1 and/or a stable Russian democracy developing peacefully.