Almost one billion people are eligible to vote in the seven-phase general elections that began on April 19 and concludes on June 1, with votes set to be counted on June 4.
Modi is seeking a record-equalling third straight term on the back of his economic record, welfare measures, national pride, Hindu nationalism and personal popularity. Surveys suggest he will easily win a comfortable majority.
His challengers have formed an alliance of more than two dozen parties and are promising greater affirmative action, more handouts and an end to what they call Modi's autocratic rule.
Friday's polling will be held for 88 of the total 543 seats in the lower house of parliament with 160 million people eligible to vote. It will be spread across 13 states and federal territories in the world's most populous country.
More than half of those 88 seats are in the southern states of Kerala and Karnataka and the northwestern state of Rajasthan.
The campaign has changed tack since the first phase and become heated as Modi and the main opposition Congress party have faced off on communal issues with Modi accusing Congress of favouring minority Muslims, aiming to dilute affirmative action and planning to impose inheritance tax.
"Congress, which used to make noise in the name of the Constitution, has now been badly exposed for its hidden agenda," Modi posted on X late on Thursday.
Congress has denied the charges and said Modi is distracting voters from real issues such as unemployment, price rise and rural distress and fears losing.
"We spoke to you, we heard what was on your mind and drafted a revolutionary manifesto," Congress leader Rahul Gandhi said in a video message on the eve of the vote. "This has been drafted by the Congress party but it is your voice."
Gandhi, former Congress president and the face of the party, is among the 1200 candidates in the fray on Friday.
Congress slumped to a historic low when it was swept out of power by BJP in 2014 and won its second-lowest number of 52 seats in 2019, with Kerala contributing the highest of 15.
The Election Commission and political parties have been worried about voter turnout due to the summer heat and wedding season in some parts of the country with turnout falling to around 65 per cent in the first phase from nearly 70 per cent in 2019.
