Ashok Gehlot voted with his MLAs in the morning.
Iin a blow to the BJP in the closely watched contest for the Rajasthan's four seats to the Rajya Sabha, MLA Shobha Rani Kushwaha was accused of voting for the Congress on Friday while a technical objection was raised about the validity of her colleague Kailash Chandra Meena's vote.
BJP-backed independent candidate Subhash Chandra, however, has demanded that the vote of Ms Kushwaha be disqualified since it was held by the poll observer.
Earlier, four MLAs from Mayawati's party who had announced a merger with the Congress in Rajasthan before playing hard-to-get ahead of the elections were among those who voted with the ruling party on Friday.
All six MLAs, who were formerly with Mayawati's Bahujan Samaj Party, came to the assembly building with Chief Minister Ashok Gehlot and cast their votes. Separately, a legal challenge to their votes also suffered a setback with the Supreme Court deciding it won't hear the case urgently.
The voting started at 9 am in the assembly building and will continue till 4 pm. Counting will start at 5 pm.
Mr Gehlot reached the assembly shortly before 9 am and the first bus with the Congress MLAs also reached the assembly with Randeep Surjewala, one of the three candidates of the Congress.
Sandeep Yadav, one of the four recalcitrant Bahujan Samaj Party-turned Congress MLAs, told NDTV, "Yes, we voted with the Congress. It is completely constitutional for MLAs of one party to merge with another if three-fourth of the party or on board."
BJP MLAs reached the assembly in two buses, while two more buses with Congress and other supporting MLAs were set to reach the assembly after some time.
Both sides had taken extensive measures to stop MLAs from being lured away. The government even had a 12-hour internet blackout in the Amer area of Jaipur to secure its flock.
The Congress has fielded Mr Surjewala, Mukul Wasnik and Pramod Tiwari while the BJP has fielded Ghanshyam Tiwari while the BJP has supported independent candidate Subhash Chandra.
Mr Chandra has made the elections challenging for the ruling Congress.
Speaking with reporters, Mr Gehlot exuded confidence that all the three candidates of the Congress will comfortably win.
He said the BJP played a "game" of fielding Mr Chandra as an independent candidate without a majority.
"Even BJP MLAs did not like him (Chandra)," he said.
BSP state president Bhagwan Singh Baba had issued a whip directing the six MLAs, who won the 2018 assembly elections as BSP candidates and merged with the Congress in 2019, to not vote for the candidates of the Congress and BJP. However, the MLAs went ahead to vote.
Some of the BSP and a few other Congress MLAs had expressed resentment last week with the Congress government ahead of the Rajya Sabha polls. The BSP members had even skipped a visit to Udaipur, where the Congress was sequestering its MLAs, and instead went for a trip to the Sariska Tiger Reserve.
In the House of 200, the Congress has 108 MLAs, BJP 71, Independent 13, Rashtriya Loktantrik Party (RLP) three, CPI(M) and Bharatiya Tribal Party (BTP) two each.
The Congress needs 123 votes to win three seats. The party claims it has the support of a total of 126 MLAs. One candidate needs 41 votes to win.