Narenda Modi, widely tipped to become India's next prime minister, suffered a setback on Friday when his closest aide was banned from election rallies and meetings after a series of speeches deemed to have stoked tensions with Muslims.
Modi, 63, a pro-business Hindu nationalist, is the prime ministerial candidate of the opposition Bharatiya Janata Party (BJP), which hopes to oust the ruling Congress Party of Rahul Gandhi with its promises of jobs and new infrastructure.
The election, the world's largest ever in which 815 million people are eligible to vote, began this week and is staggered over five weeks, ending on May 12. Results are due on May 16.
The aide, Amit Shah, who faces murder charges dating to his time serving under Modi in the state government of Gujarat, runs Modi's campaign in the state of Uttar Pradesh, which has a population larger than Brazil's and holds the keys to national power. Shah says the murder charges are a political conspiracy.
It was not immediately clear what impact a possibly disruptive ban on meetings in Uttar Pradesh by such a high profile figure would have on Modi's campaign in the state. Shah is tipped for a senior role in any Modi government.
The election commission ruled that both Shah and a minister in the Uttar Pradesh government had made statements that promoted "hatred and ill will" between religions and urged police to press criminal charges.
Speaking this month in an area of western Uttar Pradesh hit last year by deadly Hindu-Muslim riots, Shah was recorded telling voters to reject parties with Muslim candidates. He said Muslims in the area had raped, killed and humiliated Hindus.
Hindu-Muslim relations have been a key campaign issue, with critics accusing Modi of not doing enough to protect Muslims in unrest in Gujarat in 2002 that left at least 1,000 dead in revenge attacks. About 13 percent of Indians are Muslim.
Modi denies that accusation or having any religious bias. However, some of his supporters are openly anti-Muslim and Shah's canvassing has included accusing the state government of pandering to the Muslim vote at the cost of safety for Hindus.
Shah has spent time in jail fighting charges that he ordered the extra-judicial killing of a man, the man's wife and a witness who were allegedly involved in organised crime but were accused of plotting to kill Modi. Shah is out on bail awaiting trial. He denies the charges against him. The election commission applied the same restrictions on public meetings or road shows to another controversial politician, Azam Khan, who represents the Uttar Pradesh state government and has verbally sparred with Shah.
Khan has made a number of provocative statements in recent days to court the votes of Muslims - a significant vote bank in Uttar Pradesh - including saying that Muslim soldiers had fought more than Hindus in a border war with Pakistan. "These statements ... are being made with deliberate and malicious intention of outraging the religious feelings and religious beliefs of different classes of citizens of India," the commission said in a letter it made public.
The BJP is expected to emerge as the largest force after India's election but fall short of a majority. However, Indian elections are notoriously hard to predict and polls are often unreliable.