"Both the leaders are very much acceptable among the BJP cadre and the voters," BJP spokesman Mukhtar Abbas Naqvi told AFP, adding party posters will feature the faces of both men.

"We will openly project Mr. Vajpayee as the prime minister. There is no question of a successor, but it is also loud and clear that Mr. Advani is number two."

Vajpayee will be identified as the "development man" and Advani as the "iron man."

The party is to convene a brainstorming session of 100 leaders later this month to further thrash out electoral strategies.

Elections are due later this year in the Hindu-heartland states of Madhya Pradesh and Rajasthan, the capital New Delhi, Chattisgarh and the tiny northeastern state of Mizoram.

Parliamentary polls are due in October next year, but analysts believe they could be brought forward to as early as February.

The BJP has already said the popular Vajpayee will be its prime ministerial candidate for the national elections, but analysts say Advani will rise to the premiership in due course.

Elections analyst Yashwant Deshmukh said the joint projection of Vajpayee and Advani was a testing of the waters by the BJP.

"They will contest under (Vajpayee's) name because Advani alone is not in a position to sail them through," he said.

"But Vajpayee will step down after the parliament elections and pass the baton to Advani. This decision now is to test the waters in the assembly elections -- to see how the voters and allies feel about the formula. It is an attempt to define the line of control before elections begin."

Political commentator Pran Chopra agreed.

"The BJP has to accomplish a smooth transition. And what better way of doing it than projecting the party as being led by jointly by Vajpayee dressed up in one role and Advani in another role -- the two being equally necessary in government."

While Vajpayee is widely seen as the moderate face of the BJP, Advani still carries the image of a Hindu hawk, at the forefront campaign a decade ago that united Hindu radical forces across the country to build a temple in the northern town of Ayodhya where an ancient mosque stood.

The campaign led to the destruction of the mosque by mobs of Hindu zealots and cumulated in nationwide Hindu-Muslim riots.