CHENNAI: Polling in the by-election to Tamil Nadu's Radhakrishnan Nagar assembly constituency, from where Tamil Nadu Chief Minister J Jayalalithaa is seeking re-election, has begun.br br 67-year-old Ms Jayalalithaa has to fulfill a constitutional requirement of getting elected as MLA within six months of becoming chief minister. The AIADMK chief returned to the top post on May 23 after her acquittal in a disproportionate assets case, following her conviction by a trial court in Bengaluru in September last year.