Babush contested his first election in 2002 on a United Goans Democratic Party ticket from the Taleigao Vidhan Sabha constituency. His opponent was two-term sitting member of the Assembly Somnath Datta Zuwarkar from the Indian National Congress. Monserrate defeated Zuwarkar by about two thousand votes and was elected for the very first time to the Goa assembly.[4]
In the coming by-election, Babush switched sides and fought the election on an Indian National Congress ticket and won the election by defeating Silveira Agnelo Mariano of the Bharatiya Janata Party by about four thousand votes.[4] He was made a minister in the Congress government under Chief Minister Pratapsingh Rane. In the 2007 assembly elections, Monserrate was pitted against Silveira Agnelo Marian of the Bharatiya Janata Party.[citation needed]
Babush won that election by about two thousand votes[4] and was appointed the Education minister of the state under Chief Minister Digambar Kamat. In the 2012, assembly election he vacated his safe seat of Taleigao for his wife Jennifer Monserrate and contested from the Santa Cruz constituency. Monserrate won that election on a Congress ticket defeating Rodolfo Louis Fernandes by about two thousand three hundred votes.[6]
In that same election, Monserrate's wife Jennifer Monserrate also won her election from the Taleigao Vidhan Sabha constituency thus making history of sorts by having a wife and husband to be elected to the Goa Assembly.[4][7] He was expelled from the Indian National Congress in 2015 for six years for "anti-party activities".[8]
Monserrate contested the 2017 election from the Panaji (Vidhan Sabha constituency) and lost to Sidharth Sripad Kuncalienker of the Bharatiya Janata Party by about a thousand votes.[9]