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The election commission has also ordered a probe into the "leak" of the poll date after the BJP's IT cell chief Amit Malviya tweeted the election date before it was announced. Mr Malviya, who had later deleted the tweet, told the poll body that he had picked up the information from a television channel.
For the Congress, retaining Karnataka is an imperative at a time it has lost its grip on much of India. The party has just four governments - Punjab, Karnataka, Mizoram and Puducherry - compared to the BJP's 21.
The Karnataka election will be a massive test for Rahul Gandhi, who is leading the first campaign in a party-ruled state since he took over as its president in December. In his four years as Congress vice president, his leadership skills were questioned as the party lost many states.
Since BJP came to power in 2014, it has taken states like Maharashtra, Rajasthan, Haryana, Uttarakhand, Assam and Manipur from the Congress. The BJP also bagged India's most politically important and largest state Uttar Pradesh last year and last month, it also ended the 25-year Left rule in Tripura.
With the BJP, led by former chief minister BS Yeddyurappa, determined to wrest Karnataka and launching its campaign in November, the ruling Congress faces a tough challenge.
The BJP spent 85 days campaigning across the state and organized a rally in Bengaluru addressed by Prime Minister Narendra Modi. Rahul Gandhi also toured Karnataka last week. He was seen visiting a temple, a church and a mosque, besides addressing rallies.
In 2014, the BJP won 17 of its 20 seats in southern states just in Karnataka, getting massive support from the urban centres like Bengaluru and Mysuru.
In an attempt to make a dent in one of the BJP's biggest vote-bases, the Siddharamaiah government recently decided to recommend religious minority status for the Lingayats as well as for the Veerashaiva Lingay.
The BJP's chief ministerial candidate Yeddyurappa is among the state's most prominent Lingayat leaders. The BJP has accused the Congress government of hypocrisy; it points out that the previous Manmohan Singh government at the centre had rejected the plan.
The election dates and the model code of conduct may affect court-ordered attempts to resolve the Cauvery dispute. The centre may not constitute the Cauvery Management Board and tell the Supreme Court that it will affect the polls.
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