The party had only one person who they could use to reach out to these areas. All the opinion polls and media reports were suggesting that Modi's popularity had transcended regional and linguistic barriers and Gujarat's success story was being debated even in the interiors of Tamil Nadu and Andhra Pradesh although his party, the BJP, was yet to strike the imagination of the common man in these areas.
The people across the country seemed to appreciate the perceived strong and decisive leadership traits of Modi. Modi had succeeded in doing what the party could not do since its inception in 1980. And therefore, in order to grab the attention of the hoi-polloi cutting across the barriers of caste, creed and region, Modi was first elevated and then projected as the central figure of BJP's election campaign.
And this is the reason why astute politicians like N Chandrababu Naidu of AP, S Ramadoss of Tamil Nadu and others have willingly joined hands with Modi although they have nothing in common with the principles which the BJP as a party esposes. It's Modi's charisma and his track record on good governance that has galvanized them towards Brand Modi.