Back in the days when the BJP was still experimenting with Gandhian socialism and the party was not yet sure of Bal Thackeray's shrill Hindutva, the two parties had come briefly together for an election in 1983 - they lost.
But six years later, Pramod Mahajan, then the all-powerful general secretary of the patty realised that the Shiv Sena was increasingly occupying the Hindutva space and the BJP, now fully in the mood to take on the Babri Masjid could not afford to divide that vote which was already a miniscule one in a largely left of centre socialist state like Maharashtra.
But it was a random converastion with Thackeray that finally made up Mahajan's mind. Mahajan was lamenting the fact that Hindus never voted as Hindus - they were always divided by castes and other considerations. Bal Thackeray instantly shot back, "They will vote as Hindus if I ask them to."
"What do you mean?'' asked Mahajan.
"Well that was the complaint of the Maharashtrian community before the Shiv Sena was formed - that they never voted for Maharahtrians as Mahahstrians , they always chose either the Congress or the Communists. But I persuaded and compelled them to vote en masse as Maharashtrians. I know I can compel them to do so as Hindus as well.''
Mahajan took Thackeray for his word and, against the will of the RSS, forged the BJP's most lasting alliance until today with the Shiv Sena. Before their tie up the Sena never managed to win more than a single seat in the assembly at different times - MLAs Wamanrao Mahadik, Pramod Navalkar, Chhagan Bhujbal- in different years. And the BJP never managed to send more than half dozen legislators at any time to the assembly. In 1990, with the first try, the two parties managed to elect 85 legislators and displaced the socialist parties like the Janata Dal and the PWP from the opposition space, wresting the position of leader of the Opposition for themselves (Manohar Joshi of the Shiv Sena became the first LoP).
At the next election in 1995, the two parties had romped home to victory and never looked back, for the BJP went on to win the Lok Sabha with Sena support and the NDA government with more allies lasted a whole six years.
However, things went downhill for the Sena after the deaths of Mahajan and Bal Thackeray and the emergence of a more charismatic leader, Narendra Modi as the new Hindu Hriday Samrat. It was only a matter of time before the Sena would fight to retain its shared space with the BJP - and now its ally no longer finds the need to ride piggy back on the Thackerays.
The writing was on the wall long before today, but particularly after the results of the Lok Sabha elections when Modi emerged as a star and did not accommodate the Sena suitably in his cabinet.
The Sena must save its existence and the BJP needs to marginalise its ally to shed its dependence. The divorce was bound to happen.