Evo Morales is already declared as the presidential candidate of the Movement Towards Socialism (MAS-IPSP) at their party congress in Cochabamba a few months ago. The congress has also voted to expel President Luis Arce.
It created an interesting situation in which MAS was elected into power and then expelled the leader of the party who was currently president. Effectively the government went from being a MAS government to being an independent government.
But yes, there's a significant power battle going on between the left leaning socdems and the actual socialists.