Election officials said candidates from the Left Democratic Front (LDF) had forged ahead in 53 constituencies while the ruling Congress-led United Democratic Front (UDF) was ahead in 45.
The Bharatiya Janata Party (BJP), which is aiming to enter the state assembly for the first time, was at the first spot in one constituency.
The senior politicians in the lead included Chief Minister Oommen Chandy and Marxist leaders Pinarayi Vijayan and former chief minister V.S. Achuthanandan.
State BJP president Kammanam Rajashekharan was trailing at the third spot at Vatiyoorkavu.
A total of 1,203 contestants were in the fray. Most exit polls have predicted a victory for the Left.