2001–06 Tamil Nadu Legislative Assembly by-elections

UPA (2004-06) By-elections to Andipatti constituency was held in Tamil Nadu, India, on 21 February 2002. Three state assembly constituencies, Saidapet, Vaniyambadi, and Acharapakkam were held on 31 May 2002. In 2003, by-election in Sathankulam was held on 26 February 2003. During this by-election, the DMK and all the other major parties supported the Congress candidate, while only BJP supported the AIADMK candidate. This election came after the support of the Anti-conversion bill by AIADMK general secretary, Jayalalithaa and increasing tension between DMK and BJP due to the passage of the bill. The AIADMK win in Sathankulam was significant, since it completes the AIADMK sweep in by-elections after its victory in 2001. Also the anti-conversion bill was not an important factor in the congress-bastion Sathankulam, whose electorate consists of a large percentage of minorities.

Despite attempts by the opposition to delay the Andipatti by-election, due to alleged voter list irregularities, the Election Commission of India decided to have the vacant seat in Andipatti, early in February and push off the other three vacant seats, in May. Andipatti seat was made vacant by the resignation of Thanga Tamil Selvan to facilitate the election of J. Jayalalithaa, who had her corruption charges cleared in late December in 2001. Despite the fact that she could not participate in the 2001 General Elections due to her 4 nominations being disqualified, she was sworn-into office. After being released from the case, she contested this election and became Chief minister in March 2002.

As AIADMK had won 132 seats in 2001 State assembly election, even with the breakup of its previous alliance with Tamil Maanila Congress (TMC), Indian National Congress (INC), Communist Party of India (CPI), Communist Party of India (Marxist) (CPIM) and Pattali Makkal Katchi (PMK), it would have still continued to stay in power, regardless of the results in the by-election. But since Jayalalithaa was legally not allowed to run for an MLA seat in 2001, she made the decision to run for an MLA seat before swearing in as Chief Minister.

The Andipatti victory, in late February, paved way for Jayalalithaa to swear in as Chief Minister. The party also swept the by-election in late May. The PMK lost an anticipated victory in Acharappakam, a constituency with a high percentage of Vanniyars electorates. It was observed that the Dalit vote base coupled with the popularity of Jayalalithaa led to the defeat, allowing AIADMK to wrest this seat from the PMK.