Radhakrishnan's brother Ramakrishnan joined the Hindu nationalist Jana Sangh and took charge as the district chairman.

Radhakrishnan's uncle Chidambaram Athiswami Nadar contested and won the Colachal constituency in the 1977 elections on behalf of the Janata Party.

Later, Radhakrishnan's father Ponnaya Ayyappan was elected as the District President of Vishwa Hindu Parishad (VHP).

[2] Pon Radhakrishnan won the 1999 Lok Sabha election from Nagercoil constituency and became Minister of State for Youth Affairs in the Atal Bihari Vajpayee-led NDA government of 1999–2004.

[5] He had won in a Lok Sabha seat in the 2014 Indian general election, from Kanyakumari constituency by a margin of 1,28,662 votes.

Radhakrishnan participated in a BJP rally in support of Citizenship (Amendment) Act, 2019 in Nagercoil in March 2020 where he spoke of chasing away Christian priests from the district.

[12][13] He lost the Lok Sabha elections in 2019 by a margin of 2.59 lakh votes to H. Vasanthakumar from Indian National Congress.

[15] Pon Radhakrishnan claimed in 2018 that the #MeToo movement was launched by "people with perverted minds" and questioned if it was appropriate to make charges about occurrences that took place years ago.