Crimea, Dontesk and Lutansk are all Russian speaking. Now he is in the heartland of Ukraine. His best bet is to take capital and then call for a cease fire immediately. But the way things look, even if he takes the capital, Ukrainians may not agree to a cease fire.
It’s much worse than that for Putin. There is video of Ukrainian civilians being issued rifles in Kharkiv today. That’s on the border practically IN Russia. Those type of places were a mess of Ukrainian corrupt in 2014. Now Putin is powerless to take them. He has lost.