"He had joined hands with BJP in the past as per his need ... if the need arises again, he will join hands with the party," Modi, a former deputy chief minister, said. (Agencies)
He said that history was witness that the Janata Party and Janata Dal had thrice joined hands with the BJP to win power. "When they are with us BJP is not a communal party. But the moment they go away, we become a communal party."
Kumar's problem, he said, was with a 'person' and not the party and his return could not be ruled out.
On reasons for Kumar's aversion to Narendra Modi, he said that the chief minister who nourished Prime Ministerial ambitions had thought that if BJP made a lightweight PM the allies could have control over him.
"But, since Narendra Modi is not a lightweight, Kumar's calculation went wrong and he started attacking the Gujarat leader and the BJP," he said.
He claimed that Kumar knew that if he was with the BJP there was some chance of his becoming Prime Minister in future, but there was no such chance if he was with Congress.
Modi also challenged Kumar to undergo a polygraph test that then BJP President Nitin Gadkari had said Narendra Modi would not be made the party's Prime Ministerial candidate.
"I challenge him to undergo a polygraph test... If he undergoes a lie detector test, I will also offer myself for a similar test that will be covered live on electronic media."
The senior BJP leader said that according to Kumar he had fixed an appointment with Gadkari who had told him that BJP would consult NDA allies before deciding on its PM nominee.
"But, he led his party JD(U) to walk out of NDA beforehand," he said.
Modi said a lie detector test would also reveal Kumar's parleys with Union Finance minister P Chidambaram asking for a tie up between Congress and JD(U) after split in NDA.
It did not happen as the Congress was set to ally with RJD of Lalu Prasad, Modi claimed.
"He had joined hands with BJP in the past as per his need ... if the need arises again, he will join hands with the party," Modi, a former deputy chief minister, said.