I've been reading up on Russian history lately, and it has proved ripe ground for alternative history scenarios. Here's a very interesting one I found.
During the Time of Troubles when Muscovy was in total disarray, the boyars were planning to invite Wladyslaw, Crown Prince of Poland-Lithuania, to be Tsar of Muscovy. The idea was that he would eventually rule Muscovy in personal union with Poland-Lithuania. There were of course conditions to the deal- first that the privilieges of the Boyars were to be protected, and second that Wladyslaw vow to uphold Orthodox Christianity. This was later changed to stipulate that he had to convert to Orthodoxy. Eventually Zygmunt Wasa intervened and tried to simply take over Muscovy himself.
However, what if the deal had gone through? Would the people have refused to accept Wladyslaw's rule and thrown him out, or would Polewank have ensued? Would it be a combination of the two.