While studying law he had leanings to the CPI (ML), but during the anti-foreigners movement he joined a regional party.

He was the Congress candidate for the constituency of Dharmapur in 2001 and defeated the incumbent MLA and future Leader of the Opposition Chandra Mohan Patowary.

[7] His uncle Tarun Sen Deka was a leader of the RCPI and was involved in the arms struggle and later was imprisoned from 1947 to 1952.

He received international prominence after fighting a legal battle for Dhaniram Baruah, who claimed he transferred the organs of a pig into a human and was able to keep him alive for 7 days.

After all regional parties supported the Asom Gana Parishad, in 1996 he joined Indian National Congress.

Deka was the Indian National Congress candidate for the seat of Dharmapur in the 1996 Assam Legislative Assembly election.

[1] Deka was again the Indian National Congress candidate for Dharmapur in the 2001 Assam Legislative Assembly election.

Deka replied by stating the two issues could not be discussed as per law for they were sub-judice with Opposition AGP's Jagadish Bhuyan and Zoii Nath Sarma filing a PIL in the Gauhati High Court on August 25 on the incident of police firing at Rangajan in Golaghat district on August 19 and 20.

Deka introduced the Assam Protection of Interests of Depositors (in Financial Establishments) (Amendment) Bill, 2014 in the state Assembly.

[14][15] The following day on 16 December The state government will brought a resolution in the assembly by requesting the centre for proper implementation of the Assam Accord.

This was stated by Deka in the House after a discussion by Opposition AGP on the non-implementation of the accord signed in 1985 by then prime minister Rajiv Gandhi and leaders of the Assam agitation.

[2] He enjoys reading books and doing research works relating to political, economics and social aspects of 19th and 20th category.

Sarma said a case was registered at Belsor police station based on a complaint lodged by the woman's parents.

We give him 10 days time to make the whereabouts of the woman public or else we will move court, the governor and Congress president Sonia Gandhi on this issue," said Sarma.

Deka, however, denied the allegations and said according to his information, Namita had eloped with a man from a minority community to marry him.

"The police had investigated the case and filed a final report in the court saying the girl had eloped and married a man and since then they have been living together.

[20][21][22][6] Deka's remarks received much criticism, including from Chief Minister Tarun Gogoi who said it was "not in Assamese culture".

[23] A police complaint was filed against Deka, and BJP supporters held protest in front of the Congress headquarters, calling for his arrest.

[23] On 27 January 2017, the CID investigated Deka due to his alleged role in the 700 crore scam in the agriculture department.

[27][28][29][30][31] Assam Director General of Police Mukesh Sahay said that Rajarshi Deka had got his job through "unfair means".