The developing confrontation in the Ukraine between the new Ukrainian government and Russia is fascinating to watch. It is a high-stakes game of chess for all sides. From the Western viewpoint, the Ukrainians ought to be allowed to choose their own destiny. From the Russian viewpoint, losing the Ukraine from its political/economic orbit would seriously weaken Russia. And in particular, losing the Crimea would seriously impede Russia's access to the Black Sea.
Both President Obama and President Putin have a lot at stake in this confrontation. For Obama, if he looks weak and ineffectual in the long term he reinforces the already widespread perception that Democrats are weak on military and foreign policy, and in the short term he jeopardizes his party in the upcoming midterm elections. President Putin always has to placate the strong nationalist and right-wing forces in his nation, and if he fails to hold the Ukraine his own hold on power is at risk. So neither side is likely to blink early. The European Union, by contrast, is probably largely ineffectual in this whole game. They really don't have much to lose whatever the outcome.
Russian does supply the EU with much of its gas and oil, and could always cut off that supply. But that isn't as strong a card as it looks, since Russia's economy is only kept from going into free fall by the revenue it gets from its gas and oil exports. So cutting off exports to the EU would quickly produce an economic crisis in Russia.
In the long run, of course, Russia will lose this confrontation, since Russia itself is on an unsustainable downward spiral, beset with looming demographic problems, a highly inefficient kleptocratic government, a pervasive culture of corruption at all levels, an economy that is only sustained by its declining oil and gas exports, and increasing nationalistic tensions in all its old "colonial" holdings (including the Ukraine). But Putin may well win this local battle and retain at least the Crimea in Russia's orbit for the time being, if for no other reason than (a) he has more leverage than the west (including a large military force already in the Crimea), and (b) the immediate stakes are probably higher for him than for Obama or the EU - he cares more about the outcome. But winning will come at a high cost to Putin, who has tried to refashion Russia's image in the world community. That image will be seriously tarnished if he is seen to crush the Ukrainians with military force.
For America in the short term, the real issue will be if and how President Obama reacts to this crisis. He appears to have been outmaneuvered by President Putin several times recently, most recently in Syria - if he is perceived to have been outmaneuvered again in this crisis it will likely cost the Democrats dearly for years to come. If, on the other hand, he appears to outmaneuver Putin this time, it will go a long way toward strengthening the Democrat's credentials in foreign policy.
It is a fascinating chess match to watch.