The former minister, Dula Ram, joined Nationalist Congress Party, while former MLA Ashok Tanwar joined National People's Party.
Tanwar said he was feeling neglected in Congress, which had forced him to take the decision.
"I sent my resignation to the Congress state chief few days back," he said.
The former MLA had contested Assembly elections on Congress ticket in 1998 from Fagi seat and won.
However, in 2008 he contested as an independent after being denied ticket to contest the polls, but did not win.
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NCP state chief Sanjay Kumar Singh said his party will field candidates for 50 out of 200 Assembly seats.
He said those leaving Congress will be accommodated in the party but not members defecting from BJP.
NPP state chief Golma Devi said her party would field candidates for 50 seats, out of which names of 10 candidates have already been announced.
Assembly elections will be held in Rajasthan on December 1.