In an alliance lasting more than two decades he singlehandedly saw to it that whatever hurdle came, he did not allow it to break.
The alliance was shaky many times but Mahajan, a master strategist, always managed to convince Shiv Sena supremo Bal Thackeray to continue with the alliance.
In 1995 BJP-Shiv Sena did the unthinkable by forming for the first time a saffron government in Maharashtra. The alliance, though shaky at times, sailed through and completed it's tenure till 1999.
Mahajan was the only person in the BJP Thackeray trusted. The BJP will find it very difficult to replace him.
No wonder then, that when the news came out that Mahajan was sinking on Wednesday, Bal Thackeray personally went to the Hinduja Hospital to meet Mahajan and his family.
No leader from the BJP in Maharashtra, including Mahajan's brother-in-law and former deputy chief minister Gopinath Munde can aspire to his stature.
Munde was never in the good books of Shiv Sena as there have been umpteen instances of his trying to become the chief minister of Maharashtra.
Interview: Gopinath Munde
In 1999 when BJP-Shiv Sena alliance were short of five MLAs to form the government in Maharashtra, Munde was very keen that he be made the chief minister so that he could prove the majority in the house.
In fact the then outgoing Shiv Sena chief minister, Narayan Rane openly said that the alliance could not be formed because of Munde's personal ambitions.
Sena gives up, asks BJP to take reins
The alliance could not form the government as Mahajan was busy with politics at the centre. He came down later to Mumbai only to patch up between the two warring parties after the Congress and Sharad Pawar's Nationalist Congress Party formed an alliance government.
"His loss is irreplaceable to all of us," said former state chief minister and Shiv Sena leader Manohar Joshi after Mahajan's death.
Mahajan was an astute politician who knew that an Hindutva agenda and a strong alliance with the Shiv Sena was the only way to rule Maharashtra.
After Uddhav Thackeray took the reins of Sena he interacted with senior BJP leaders like L K Advani and A B Vajpayee but there was no enmity with Mahajan.
"He always has been an inspiration to many BJP workers in Maharashtra. It is a great personal loss to me and the party," said BJP Maharashtra General Secretary Pramod Tawde.
The first test for the alliance will come in 2007 when Mumbai's municipal elections will be he held.
"In his death, the country has lost a skilled organiser, a forceful orator and an aggressive representative of its youth," Vajpayee said in his tributes to Mahajan.
Complete coverage: Pramod Mahajan shot