Shiv Sena chief Bal Thackeray set the cat among the pigeons as he pitched for BJP leader Sushma Swaraj as a "great choice" for the prime minister's post.
"There is only one person who is intelligent and brilliant - Sushma Swaraj..." Thackeray told Sena mouthpiece Saamana on Sunday when asked about possible BJP candidate for the top post.
The BJP was cautious in its reaction but its NDA partner Janata Dal (United) said the prime ministerial candidate would be decided by all the alliance partners, not just the Sena.
This is the first time that an NDA constituent has openly come out in support of a candidate.
A few weeks ago, another ally, the JD (U) had done the opposite.
Senior leader and Bihar chief minister Nitish Kumar virtually vetoed his Gujarat counterpart Narendra Modi's candidature, indicating "anybody but him".
"She (Swaraj) would be a great choice for PM's post. She is a deserving, intelligent woman… I think she will make a dashing prime minister," Thackeray said in Part 3 of a marathon interview that appeared on Sunday.
The endorsement comes a few days after the leader of opposition in Lok Sabha paid the Sena chief a "courtesy visit" at his Mumbai home.
"BJP has many leaders who are competent to become the prime minister… a decision will be taken by the BJP and other NDA partners at the time of elections," party vice-president Mukhtar Abbas Naqvi said.
NDA convener and JD (U) leader Sharad Yadav said all the alliance partners would together pick the candidate.
The Congress accused the NDA of "counting chickens before they hatch".
"The larger NDA suffers from a unique malady of anointing prime ministers without waiting for people's verdict," spokesperson Manish Tewari said.
Sena chief was also critical of BJP veteran LK Advani's claim that a non-UPA and non-NDA government was a distinct possibility in 2014.
"What can we expect from persons like him? Wonder why he said such a thing...," Thackeray said of Advani's early August blog post.
With inputs from Mumbai