approval of his parliament (tee hee) to send troops into Ukraine and, to top it off, he's been asked by the government of Crimea to intervene. He's got plenty of muscle down there already. All he needs now is something akin to a Reichstag Fire that he can blame on the Kiev guys and he's away to the races.
Will he or won't he? The "please invade us" card does have a limited shelf life although it's also renewable. Then there's the question of the Ukrainian army. Although it's only about a quarter the size of Russia's, it's still a substantial force in a territory the size of Ukraine. There's a large percentage of ethnic Russians in the Ukrainian army but analysts seem to conclude they would remain loyal to Kiev, not side with Moscow.
Now we wait and see.
Update: the federal government has recommended that Canadians in Crimea leave Ukraine