I predict not just a bare victory but a sweep in favour of the Lalu-Nitish alliance in the coming Bihar elections. This is based on simple mathematics.
As I had said in an earlier post, voting in most states in India, including Bihar, is on the basis of caste and religion. The exception to this rule is when there is a wave.
In the May 2014 elections there was a Modi wave, as people, particularly the youth, were captivated by the magic slogan of 'vikas', which promised millions of jobs to our huge population of unemployed youth, whose voting age had been reduced from 21 to 18 by a Constitutional amendment of 1988.
This slogan, however has proved hollow, as jobs have not been created, and the youth have been left high and dry. While there has been a lot of big talk, hardly anything has been done by Modi except stunts like 'Swatchata Abhiyan' ( I visited Varanasi yesterday and found it as dirty as ever, and I spoke to many citizens there who said the same ), Yoga Day, etc and meaningless foreign trips which must have cost a huge amount of money and whose end result is ' khoda pahaad, nikli chuhiya'.
So the Modi wave has totally dissipated, and now voting in Bihar will be on the traditional lines of caste and religion.
Here are the caste demographics of Bihar which I got from the net :
OBC/EBC 51% ( Yadavs -14%, Kurmis- 4%,( EBCs - 30% -includes
kushwahas - 6% Koeris -8%, Teli-3.2%))
Mahadalits* + Dalits(SCs) 16%
Forward caste 15% (Bhumihar -3%, Brahmin-5%, Rajputs- 6%, Kayasth- 1%)
Adivasis(STs) 1.3% 
Others 0.4% (include Christians,Sikhs,Jains)
As per, 2011 Census of India , Scheduled Castes constitute 16% of Bihar's 104 million population. The census identified 21 of 23 Dalit sub-castes as Mahadalits. Mahadalit community consists of the following sub castes - Bantar, Bauri, Bhogta, Bhuiya, Chaupal, Dabgar, Dom (Dhangad), Ghasi, Halalkhor, Hari (Mehtar, Bhangi), Kanjar, Kurariar, Lalbegi, Musahar, Nat, Pan (Swasi), Rajwar, Turi, Dhobi, Pasi, Chamar and Paswan (Dusadh). Paswan caste was initially left out of the Mahadalit category. Adivasis (Scheduled Tribes) constitute around 1.3% of Bihar population. Tribals include Gond, Santhal and Tharu communities in Bihar.
Extremely Backward Class (EBCs) are also sometimes referred to as Most Backward Class(MBCs). There are 130-odd EBC castes in Bihar.
Yadavs and Kurmis constituting 19% and Muslims about 17% will solidly vote for the Lalu-Nitish alliance, which makes it 36%. Muslims will vote for it ( despite Owaisi, who is regarded as a BJP vote splitter by Muslims, and who will therefore not be misled by him ) because Muslims are feeling very insecure after love jihad, ghar wapasi, speeches of Adityanath, Sadhvi Niranjan Jyoti ( calling them haramzadas) and incidents like in Muzaffarnagar, Ballabhgarh, and the latest one at Dadri.. So they will solidly vote for the alliance.
A section of the other backward castes, say 8-10%, will also vote for the alliance, as Lalu has successfully described it as a fight between the backwards and the forward castes.
Thus the tally of the Nitish-Lalu aalliance comes to about 45% votes, which represents a sweep ( BJP got a majority in the Lok Sabha with only 31% votes )
As regards, the NDA, its support is from the upper castes, and a section of EBCs( also called MBCs ) and a section of dalits, because of Paswan, Manjhi and Upendra Kushwaha.
The upper castes in Bihar, as can be seen from the above chart, are altogether only 15%. Paswan does not have the support of all the dalits ( who are divided into a large number of sub castes) in Bihar, unlike Mayawati who has the support of almost all the dalits in U.P. So he may get the NDA about 6-7% votes. Manjhi may get 7-8% MBC votes, and Kushwaha may get 4%votes.
Thus the total tally of NDA votes is 15+7+8+4=32%
There is clearly going to be a sweep in favour of the Mahagathbandhan in Bihar