A post-election tussle between the BJP and Shiv Sena may push formation and swearing-in of the new Maharashtra government to the end of the month. The two parties, who contested the Assembly elections together and secured 161 seats in the 288-member house, are believed to be squabbling over distribution of portfolios. The Sena, which won 56 seats to the BJP's 105, has even hinted at the Chief Minister's post, suggesting a two-and-a-half year rotation between the parties.