An estimated 4.93 lakh strong electorate is expected to decide the poll prospects of 33 candidates.
Authorities have set up 694 polling stations for the voting, which will be held between 8 am to 5 pm, Special Officer (Elections), Manoj, in Karnataka Chief Office said.
The bypoll was forced on these constituencies following defection of Congress and JD(S) MLAs to the ruling BJP, whose numerical strength in the assembly had shrunk after eleven of its rebels and five independents supporting the B S Yeddyurappa govenment withdrew support in October last.
While M C Ashwath of JD(S) quit his party and assembly membership in Chennapatna Constituency, S V Ramachandra and M Narayanaswamy of Congress resigned their Jagalur (ST) and Bangarpet (SC) seats to defect to the saffron party.
Interestingly, Chennapatna constituency is facing election for the third time since 2008. C P Yogeshwar, elected on a Congress ticket but defected to BJP in 2009, lost to JDS candidate Ashwath in the bypoll. However, Ashwath also crossed over to BJP leading to another bypoll.
BJP has fielded Yogeshwar in Chennapatna after Ashwath refused to take the plunge into the electoral battle.
Narayanaswamy and Ramachandra in Bangarpet and Jagalur are seeking relection on BJP tickets.
While Congress and JD(S) have been pulling out all stops to defeat BJP candidates appealing to the electorate "not to encourage defectors" and teach BJP a lesson, the ruling party is seeking votes on the twin planks of government stability and development.
Counting will be taken up on May 13. Chennapatna has highest number of 15 aspirants, followed by ten in Bangarpet and eight in Jagalur. Jagalur has a total electorate of 1,52,204, Bangarpet 1,53,609 and Chennapatna 1,87,803.