CPI would provide all help including propaganda to the CPI-M candidate, CPI state Secretary D Pandian told reporters here.
CPI-M has fielded K Annadurai to take on AIADMK nominee S Valaramthi and DMK's N Anand for the seat which has fallen vacant after the disqualification of AIADMK chief Jayalalithaa following her conviction in an assets case.
The constituency is witnessing a multi-cornered contest with the BJP-led NDA too fielding its nominee for the poll.
Pandian also took exception to Union Finance Minister Arun Jaitely meeting Jayalalithaa recently. Traditionally, no minister would meet persons whose case in progress in court, he added.
"The present AIADMK ruling is much better, when compared to other states," he said.