In a setback to AAP ahead of Saturday's Haryana Assembly polls, the party's Nilokheri (reserve) seat candidate Amar Singh joined the Congress.
After joining the party, Singh on Wednesday said only Congress can defeat the BJP government which has been "unjust to farmers, women, Dalits, and minorities".
He joined the Congress here in the presence of Partap Singh Bajwa, Leader of Opposition in the Punjab Assembly, the party said in a statement.
Bajwa formally inducted Singh into the party, it added.
The Aam Aadmi Party (AAP) is part of the INDIA bloc, but is contesting the Haryana elections on its own after the talks between the Arvind Kejriwal outfit and Congress last month to forge an alliance for the state polls did not materialise.
The fresh setback to the AAP in Haryana comes days after its Faridabad candidate Pravesh Mehta joined the ruling BJP on September 28.
Mehta had joined the BJP in Faridabad in the presence of Union Minister Krishan Pal Gurjar, who is the BJP MP from Faridabad, and Haryana BJP leader Vipul Goel.
Meanwhile, welcoming Singh, Bajwa said he has joined the party unconditionally and "has extended full support to Congress candidate (from Nilokheri) Dharampal Gondar".
Bajwa also mentioned that Singh is popular within the Sikh community in Nilokheri.
Singh said that Haryana is witnessing a direct fight between the Congress and the BJP. The same situation exists in Nilokheri, he added.
The former AAP leader said the main goal at this moment is to get rid of the BJP government, "which has been unjust to farmers, women, Dalits, and minorities, and only Congress can achieve this".
He added that had he continued contesting the election, it would have directly benefited the BJP. To ensure that the vote is not divided, he decided to join the Congress.
(This report has been published as part of an auto-generated syndicate wire feed. Apart from the headline, no editing has been done in the copy by ABP Live.)