There are 300,000 protesters on the streets of Kiev tonight and clashes have occurred across the city with some demonstrators having seized control of the City Council building with crowds continuing to mount. Demonstrations in other cities have seen 20,000-30,000 on the streets. The opposition is calling for fresh elections and the resignation or impeachment of embattled President Viktor Yanukovych in response to the U-turn over the EU association agreement and the refusal to release his former political rival Yulia Tymoshenko. Many are seeing this as a re-emergence of the bitter East vs. West divide that led to the Orange Revolution in 2004 and a serious 'backfire' to Russian pressure for a rejection of the agreement. According to the OpEd I've listed below and some other sources tomorrow will be a major test as momentum appears to be on the side of the protest movement with calls for 400,000 or more to hit the streets and reach the Presidential Palace despite a ban on protests in the capital vicinity. According to the writer there are rumors circulating that Yanukovych will call for a caretaker cabinet as a strategic measure to buy time leading up to fresh elections.
This is very interesting as it could lead to a rapid collapse of the pro-Russia position in Ukraine and undo much of the progress that they have made since the arrest of Tymoshenko. What was supposed to be a culminating measure away from the EU and the West may be the trigger that brings it all down. Of course it might all fizzle out or fall to a crackdown but in the wake of so many wave protest movements in the past decade (including one in Ukraine) I don't think it should be discounted so readily.
BBC News - Clashes amid huge Ukraine protest against U-turn on EU
The Orange Revolution MKII