The BJP should have welcomed Mr Gandhi's declaration of his prime ministerial ambitions, the NDA ally said, adding that it was against democracy to make fun of Mr Gandhi over his remark.
The BJP should have challenged him to defeat it in the 2019 general polls.
Mr Gandhi had said two days ago that he was ready to occupy the Prime Minister's post if his party wins the most seats in the 2019 Lok Sabha polls, making known his ambition for the top executive post.
Reacting to the comment, PM Modi wondered whether the country would ever accept such an "immature and naamdar (famous)" leader for the post.
Rebuking the BJP for criticising Mr Gandhi's comments, the Sena said people would decide if the Congress president would become the prime minister in 2019 or face defeat.
"However, saying that he (Gandhi) is eager to become the prime minister or making fun of him is against democracy," it said in an editorial in the party mouthpiece 'Saamana'.
"If there is democracy left in the country, the BJP should have welcomed Gandhi's statement and challenged him to defeat it in 2019," the Sena said.
Lavishing praise on the 47-year-old Congress leader, the Sena said, "Rahul Gandhi today is not the same as he was in 2014. He has become a strong-minded person after bearing criticism. He can pose a challenge to the BJP in 2019 and the Gujarat Assembly polls have proved this."
Mr Gandhi's opponents have to agree that he has maintained a "certain degree of political class", the Sena said.
Taking a jibe at PM Modi, it said, "The PM has started remembering his 'alliance dharma' now. We are happy to hear that."
It said the BJP thinks there is no dialogue between the Congress and its allies. But what has been the BJP's level of interaction with its coalition partners and how many decisions in the interest of the country have been taken by working together, the bickering ally sought to know.
Allies were being "stabbed in the back" with the sword of power, which the BJP got due to the collective efforts of NDA partners, the Marathi daily said.
If the BJP asks how Mr Gandhi can be the contender for the prime ministerial post when there are seniors in the Congress and UPA allies, then BJP stalwarts like LK Advani and Murli Manohar Joshi will be the right persons to answer, the Sena quipped.
"Similarly, Modi and (BJP chief) Amit Shah appointed the (country's) president without talking to NDA partners," the publication claimed.
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