Voting in a key Indian state opened Saturday amid dirty tricks claims by the two leading parties after nearly 10,000 voting cards were seized by election authorities.
The opposition Congress party, which has dominated India's politics in the seven decades since independence, is fighting to retain control of its last major state, Karnataka, amid a fierce onslaught by Prime Minister Narendra Modi's ruling Hindu nationalist party.
Voting was postponed in one constituency after the discovery of the voting cards, which authorities suspect were obtained through bribes. Police have launched an investigation.
The state election commission said there was a "planned design to induce the voters, thus attempt to vitiate the poll process" in Rajarajeshwari Nagar district of the state capital Bangalore.
Congress and Modi's Bharatiya Janata Pary accused each other of being responsible. Voting in the district was put back to May 28.
Tens of thousands of security personnel have been deployed across the state of 65 million people for voting. The result, which will have a major impact on campaigning for a national election next year, will be announced on Tuesday.
Voting started slowly in Bangalore, India's global IT hub, after a rainstorm on Friday again exposed the city's over-stretched infrastructure with massive traffic snarls, waterlogging and overflowing drains.
But the two parties urged voters to brave the disruption and turn out.
"I appeal to all office bearers and workers of the Congress party in Karnataka to provide all possible assistance to those affected by heavy rains," Congress leader Rahul Gandhi said in a Twitter statement.
"Our polling booth teams must remain alert and must help voters facing difficulties in reaching polling booths," he added.
Modi also issued an appeal.
"Urging my sisters and brothers of Karnataka to vote in large numbers today. I would particularly like to call upon young voters to vote and enrich this festival of democracy with their participation," the prime minister said on Twitter.
The two leaders have embarked on an angry campaign targetting each other with personal attacks. Local issues such as the state's infrastructure crisis have barely featured.
But Karnataka is crucial for both parties.
Congress is anxious to reverse its political fortunes so it can mount a strong challenge in next year's election.
If it loses Karnataka, Congress will only have two small states, Mizoram and Punjab, and the small territory of Puducherry which together account for about 2.5 percent of India's population of 1.25 billion.
The BJP and its allies hold states with about 70 percent of the population.
But Modi's party needs a breakthrough in the south of India.
The prime minister has has faced allegations of bias towards the northern, western and central regions where his Hindu nationalist BJP is dominant.
Modi has focused his campaign on national pride, the economy and his aggressive foreign policy. He has also attacked Gandhi's Italian ancestry and family's privileged history. His mother, Sonia, is Italian and the Gandhi-Nehru dynasty has provided three prime ministers since 1947.
Congress has instead focused on building up the region.
It has also questioned the BJP's selection of B.S Yeddyurappa as its candidate for chief minister. The 75-year-old has in the past faced corruption allegations.
Some polls have predicted a hung state assembly with a regional party, Janata Dal, led by 84-year-old former prime minister H.D Deve Gowda and his son, playing a key role in forming the next state government.