On a wet Friday night in a hall in north Mumbai, a party’s footsoldiers sat on the floor. The underlining message from local leaders was specific: Tell your community of nervous voters — all North Indian settlers in Mumbai — not to fear our ally, the Shiv Sena.The BJP men understood only too well. They were all Uttar Bharatiya or of North Indian origin. It’s a massive voter base growing alienated from the saffron combine, insecure and unsure of the Sena’s stance of ‘Mumbai for Mumbaikars.’It was after losing Mumbai at the Lok Sabha polls that the BJP woke up to losing the migrant vote and their faith.So, a low-profile but high-stakes plan is now underway. ‘‘We’ll identify cadres who speak Bhojpuri and Hindi to explain to voters that Shiv Sena now respects North Indians,’’ said R.U. Singh, former president of BJP’s Uttar Bharatiya Janta Parishad at the meeting in Kandivali.The BJP is identifying communities for special campaign attention in select gatherings of 50 upwards for house-to-house canvassing. Singh says his people have no problem with BJP. ‘‘But they misunderstand the Sena. They are insecure.’’He’s part of 10 new groups within BJP, quietly mapping Mumbai’s settlers — from Uttaranchal, Bihar, UP, Gujarat, Rajasthan, Bengal and South.The strategy is said to be the brainchild of Pramod Mahajan, in-charge of the party’s state election planning. On August 26, Mahajan will dine with select Uttar Bharatiya cadre and ‘‘respectable’’ community members at Bandra, says Singh.