Polling began at assembly premises in the state capitals at 9 am and will continue till 4 pm.
While 30 of the total 57 seats in the current round of biennial elections have already been decided without a contest, Saturday's polls will decide the fate of remaining 27 as BJP and Congress will be engaged in a keen battle for some of the states.
Allegations of bribing JD(S) and Independent MLAs have marred the polls in Karnataka but the Election Commission has rejected demands for cancelling them.
Uttar Pradesh
All eyes are on Uttar Pradesh, where elections are being held to 11 seats. Interest is centred around a fight between Sibal and a BJP-backed independent socialite Preeti Mahapatra.
Sibal will need the support of BSP, which has 12 votes more than necessary for the success of its own candidates Satish Chandra Mishra and Ashok Sidharth.
BSP supremo Mayawati has maintained suspense over her party's support in Uttar Pradesh. But Sibal can draw heart from the fact that she has already extended backing for a Congress candidate in Madhya Pradesh by promising one vote required for senior Supreme Court lawyer Vivek Tankha, fielded by Congress. Congress has 29 MLAs and needs the backing of five more to see Sibal through.
The ruling SP has fielded seven candidates including Amar Singh and Beni Prasad Verma, who both rejoined the party recently, and Reoti Raman Singh. Its seventh candidate is, however, short of 9 first preference votes. SP has been promised backing by Ajit Singh-led RLD which has 8 MLAs.
The BJP has fielded Shiv Pratap Shukla, who is sure to get elected on its own 41 MLAs, and has offered 7 surplus votes to Mahapatra.
Karnataka
Karnataka, where four seats are up for grab, is poised to witness a battle between the ruling Congress and the JD(S). Union Minister Nirmala Seetharaman of BJP, who needs just one vote more than the party's strength of 44, and former union ministers Jairam Ramesh and Oscar Fernandes of Congress are sure of victory.
With 122 members, Congress has a surplus of 33 votes after ensuring the victory of Ramesh and Fernandes. It has fielded former senior IPS officer K C Ramamurthy as its third candidate for which it requires 12 more votes.
With 40 members, dissidence-hit JDS is in an unenviable position as five MLAs have virtually raised a banner of revolt amid reports that they might indulge in cross voting to help Congress.
JDS needs five more votes for its candidate B M Farooq, a corporate personality, to sail through but is struggling to keep the herd together.
The JD(S) saw open defiance when four of its members stayed away from the legislature party meeting on Thursday, called to chalk out a strategy for the victory of the party candidates in both Rajya Sabha polls and Legislative Council polls.
Haryana
The other state where there is keen interest in the contest is Haryana, independent candidate R K Anand has the backing of unlikely rivals -- Congress and INLD.
To checkmate BJP, which is sure of sending Union Minister Birender Singh to the Upper House, the Congress on Friday extended support the support of 17 MLAs to Anand, who also has the backing of INLD's 19 and Akali Dal's lone MLA.
A candidate in Haryana needs 31 votes to go to Rajya Sabha. The contest is between Anand and BJP-backed Independent candidate, Subhash Chandra, a media magnate, who has the declared support of BJP's 16 surplus votes. Anand appears to have an edge.
Madhya Pradesh
A Congress-BJP encore is also on the cards in Madhya Pradesh where election is being held for three seats.
While ruling BJP, which has 164 votes, is assured of victory of its candidates M J Akbar and Anil Dave, a fight is on for its third candidate Vinod Gotia, who faces a tough challenge from Vivek Tankha of Congress, as he needs 10 more than the 48 surplus votes his party has.
A candidate in Madhya Pradesh needs 58 votes for victory. Tankha, whose party Congress has 57 votes, appears comfortably placed after BSP announced the backing of its four MLAs.
Rajasthan
Rajasthan is another state where Congress, with 24 MLAs, has forced a contest by backing an Independent candidate Kamal Morarka. A candidate needs 41 votes to win.
With 160 members in Raqjasthan Assembly, the BJP is certain to ensure the victory of Union Minister M Venkaiah Naidu, its Vice President Om Prakash Mathur, former RBI official Ram Kumar Sharma and Harsh Vardhan Singh, a member of the erstwhile Dungarpur royal family.
The fourth BJP candidate needs only four more votes to sail through, which the party expects to get from two MLAs of NUZP and three Independents.
Jharkhand
In Jharkhand also, a keen contest is possible where a united opposition can upset the ruling BJP's calculations. But its first candidate and union minister Mukhtar Abbas Naqvi is sure of victory.
The BJP has 43 MLAs on its own and enjoys the support of six more MLAs of its allies.
JMM supremo Shibu Soren's son Basant is pitted against BJP's Mahesh Poddar. However, if Congress (6), RJD and rest of the opposition come together and back the JMM candidate, Basant can look at victory.
Uttarakhand
Uttarkhand, where election is only for one seat, Congress nominee Pradeep Tamta is set to sail through needing just two additional votes apart from his party's 26 and ally PDF's six. He has been assured that by PDF which is also part of the ruling coalition. The winning candidate has to secure 30 votes.
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