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Mr Thackeray said on Thursday that the Sena will no more contest elections in partnership with the BJP starting with next month's key civic polls in Mumbai and nine other cities of Maharashtra.
"We ministers carry our resignations in our pockets," said the Sena's Ramdas Kadam today, stating that Uddhav Thackeray will decide at an "opportune time" whether the Sena will withdraw from the Maharashtra government and the centre, where it has three ministers.
The Shiv Sena has 14 ministers in the government of the BJP's Devendra Fadnavis in Maharashtra. The party's 63 legislators support single-largest party the BJP, which has 122 legislators.
If the Sena withdraws support, Chief Minister Fadnavis' government will be in a minority - the halfway mark in the state assembly is 145 seats - and the NCP's 41 legislators can bridge the gap.
"I will not bend in front of anybody. If somebody thinks we are lesser than them, we will displace them," said Uddhav Thackeray on Thursday, accusing the BJP of "backstabbing" his party and ending the suspense over whether the allies would contest the elections to Mumbai's civic body BMC together.
Chief Minister Devendra Fadnavis' only comment so far has been this tweet: "Power is the means for change not the eventual goal. Change will happen. It will happen with you or without you." During failed negotiations over seat-sharing he made it clear that the Sena must acknowledge the BJP's new status as the bigger party in the state.
The Sena and the BJP has fought the last BMC elections as allies. The Shiv Sena had won 75 of the 227 seats, with the BJP winning 31, the Congress 52 and the NCP 13. The BMC or Brihanmumbai Municipal Corporation is India's richest civic body.
But since the last BMC election in 2012, when the Congress-NCP ruled the state, political dynamics in the state have altered drastically. The BJP, Shiv Sena's junior partner for years, has emerged as the state's number 1 party.
The BJP followed up a big win in the 2014 national election by emerging as the largest party in the Maharashtra assembly elections a few months later. In by-elections and local polls since the party has continued to make gains at the cost of the Sena, Congress and NCP.
The BJP's coming of age in Maharashtra has troubled the Shiv Sena, which had in broken off the alliance ahead of the 2014 Maharashtra elections, but returned to participate in the government. But Uddhav Thackeray and his party leaders have lost no opportunity to criticise the Narendra Modi government at centre, most recently joining the opposition in attacking it over its handling of demonetisation.
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