The death of A. Nesamony in 1968 led to the by-election in Nagercoil constituency. Realising the popularity of Kamaraj in this constituency and the pontential danger posed by Kamaraj's election after the Indian National Congress party's debacle in 1967 election, C. Rajagopalachari wrote in Swarajya, the magazine of the Swatantra Party about the need to defeat him and appealed to C. N. Annadurai to support M. Mathias, the Swatantra Party candidate. Annadurai deputed M. Karunanidhi, the then Minister for Public Works to Nagercoil to work in support of M. Mathias. Despite the efforts, Kamaraj won decisively with a 1,28,201 votes margin on 8 January 1969.
Nagercoil Lok Sabha constituency used to be composed of the following assembly segments: