The vote pits Modi's Bharatiya Janata Party (BJP) against an alliance of two dozen opposition parties which is challenging him with promises of increased affirmative action, more handouts and what they say is the need to save democratic institutions from Modi's dictatorial rule.
The gigantic exercise involving almost one billion voters begins on Friday and will be spread over seven days across the world's most populous country in the peak of the summer heat. It ends on June 1 and votes will be counted on June 4.
On Friday, in the largest of the seven phases, 166 million voters in 102 constituencies across 21 states and territories will vote.
Surveys suggest BJP will easily win a majority even though voters have serious concerns about unemployment, inflation and rural distress in the world's fastest-growing major economy, with the spotlight being on whether BJP can improve on its 2019 victory and by how much.
"In the next five years, we will take our nation into the top three economies of the world, launch a final and decisive assault against poverty, open up newer avenues of growth ... unveil the next generation of reforms, and take a number of pro-people decisions and actions," Modi wrote in the BJP's election manifesto.
If he wins, Modi will be only the second Indian prime minister to be elected three times in a row, after post-independence leader Jawaharlal Nehru.
The opposition INDIA alliance says the election is an ideological battle being fought to stop the BJP from ending the constitution and democratic system.
Rahul Gandhi, leader of the main opposition Congress party, said the BJP always seeks to divert attention from major issues such as unemployment and price rises.
"Sometimes the PM goes underwater in the ocean and sometimes he is on a seaplane but does not talk about issues," Gandhi said, referring to Modi's widely publicised engagements in recent months.
While the alliance has struggled to forge unity and field common candidates against the BJP, it has accused the government of denying it a level playing field by arresting opposition leaders in corruption cases and making huge tax demands ahead of the vote - charges the government denies.
