The newly formed love story between LSP and Left is a double edged sword. By default it is deemed to a breakup because of the sharp differences between their ideologies (there are too many to name, for example, Left would oppose FDI in retail, and LSP would support).
The only thing that will keep them together is the need. LSP can’t fight elections alone, and they desperately need someone to join hands with. The perception is that Left are only the other cleanest party among AP. On the other hand, Left parties are becoming old by the day, and they desperately need some new facelift. Since they are trying to distance from TDP, and they can’t join hands with even more corrupted parties like YCP; LSP probably will help them get closer to the youth.
I think the key factor to the success or failure of this alliance will be in the hands of LSP. Left being an (inter)national party, and an old one too, they are not going to change their stance on the issues. That means LSP needs to be flexible. On the other hand, both parties can go on the alliance, purely for elections.