BJP and the Shiv Sena have been rival partners in an alliance that is 35-year-old. They came together for the first time in 1984 thanks to an anti-Congress front engineered by Sharad Pawar, the powerhouse Maratha politician. Sharad Pawar had not included the Shiv Sena in the multi-party coalition as he and then Sena chief Bal Thackeray were vying for same Maratha vote bank. Thackeray had the additional plank of Hindutva.
The BJP was made part of the alliance but had a very weak organisation in the state at that time. The party was only four-year-old then. Bal Thackeray arrived at an agreement with the BJP leadership of LK Advani and Atal Bihari Vajpayee and fielded Shiv Sena candidates on BJP’s election symbol in the 1984 election.
Bal Thackeray, by then, had generated significant Hindutva sentiments in Maharashtra for the two parties to come together. A formal alliance was formed for the 1989 Lok Sabha election, in which the BJP was to contest on 22 of the 48 parliamentary seats in the state and Shiv Sena on 6.
Hindutva was the glue that bound them together and presented them as one unit to the voters of Maharashtra, election after election. An average voter in Maharashtra does not differentiate between the Shiv Sena and the BJP at state and national level believing they would be one post-election even if they contest separately.