Opinion polls never predicted BJP/NDA comming to power in the current situation.
BJP is yet to add new alliances after his announcement as PM candidate.
Communists --
Mayawathi
Mulayam
Mamtha
Jayalalitha
Nithish
Naveen Patnayak
Jagan Mohan Reddy
The above are neither pro BJP and nor pro congress.
So a Hung parliament with third front is bad for the country with each one bargaining for their own benefits and portfolio.
Let me give some explanation:-
Communists -- They might not join NDA/UPA
Mayawathi -- Pure opportunist, She will join if offered some good portfolio and also if agreed to clear all CBI cases on her
Mulayam -- Same as Mayawathi
Mamtha -- She will definately join NDA after polls, if BJP has sufficient amount of seats
Jayalalitha -- same as Mamtha
Nithish-- His political career is over. He will suffer biggest defeat of his political life..Mark my words
Naveen Patnayak-- He wont join NDA
Jagan Mohan Reddy-- Remove CBI cases he will join any party.. Affinity towards NDA is more now