Three independent candidates withdrew their nominations on Thursday, said the Election Commission officials.
A total of 76 candidates had filed nominations for the bypoll. The nominations of 45 of them were rejected, including Communist Party of India-Marxist (CPI-M) candidate Shekhar Rao.
The by-poll in Huzurnagar is necessitated by the resignation of state Congress chief Uttam Kumar Reddy from Assembly following his election to Lok Sabha from Nalgonda constituency in the recent general elections.
The main candidates remained in the fray include Uttam Kumar Reddy's wife and Congress candidate Padmavathi Reddy, ruling Telangana Rashtra Samithi's Saidi Reddy, the Telugu Desam Party's Chava Kiranmai and the Bharatiya Janata Party's K. Rama Rao.
It is likely to be a direct fight between the TRS and Congress candidates.
The Communist Party of India (CPI), which is not contesting the by-poll, has declared support to the TRS. Telangana Jana Samithi (TJS), which is also staying away from the contest, announced support to the Congress. With the CPI-M candidate's nomination being rejected, the TDP has sought the party's support.
In the Assembly elections held in December 2018, the TDP, the CPI and the TJS had contested the polls in alliance with the Congress. However, the four-party People's Alliance failed to stop the TRS from retaining power with a massive majority.
The Congress, which won 19 seats, has since lost 12 of its MLAs to the TRS. One of TDP's two MLAs also defected to the ruling party.
( With inputs from IANS )