The Janta Dal United suffered a major setback in Arunachal Pradesh as six of the seven MLAs shift from the Nitish Kumar party to its ally BJP.
The JDU now has just one MLA in the 60-member Arunachal assembly. Along with an MLA of the People's Party of Arunachal, the BJP now has 48 members.
The JDU MLAs who quit are Hayeng Mangfi, Jikke Tako, Dongru Siongju, Talem Taboh, Kanggong Taku and Dorjee Wangdi Kharma. Three of them had been suspended and served notices last month for anti-party activity.
The BJP's state unit chief Biyuram Wahge said the development proved people's faith and trust in the leadership of Prime Minister Narendra Modi and Chief Minister Pema Khandu.
"The tally entitles us to the status of the main opposition party. But we will offer full support to the BJP government in that state. Even if we get the opposition party status, we will be a friendly opposition," JDU leader KC Tyagi had been quoted as saying by news agency PTI.
The strength of opposition has now gone down to 12 - four each from Congress and National People's Party, one from the JDU and three Independents.
In the October-November election, the National Democratic Alliance (NDA)'s majority in the 243-member assembly was powered by the BJP's 74 seats. The JDU finished at number 3 - after Tejashwi Yadav's RJD and BJP -- with its tally dropping to 43 from 71 in 2015.