Mr Kejriwal is an anti-corruption campaigner of leftist sympathies whose Aam Aadmi or Common Man party has caught the public's imagination over the past year and whose popularity could limit the scale of Mr Modi's expected election victory.
Both, however, come from relatively humble backgrounds. Mr Modi, a professional politician who has run the state of Gujarat for the past 12 years, boasts that his father was a tea-seller.
Mr Kejriwal is a former tax inspector and engineer's son who won entry to one of the highbrow Indian Institutes of Technology and passed the civil service exams through his own efforts.
Those life stories are in stark contrast to the privileged upbringing of Rahul Gandhi, the Congress figurehead and son of party leader Sonia Gandhi.
(Read more: India to kick off world's biggest election on April 7)
Descended from no less than three Indian prime ministers – Jawaharlal Nehru, Indira Gandhi and Rajiv Gandhi – Mr Gandhi has never been in government. Widely regarded as amiable but ineffective, he is nevertheless marketed as a future prime minister by virtue of his illustrious forebears.
"Both Modi and Kejriwal – part of their attraction is precisely that they are outsiders, and have no political lineage," says Ashutosh Varshney, a political scientist and author of a new book on Indian democracy. Famous names that once impressed rural Indians have less impact in the country's fast-growing cities, he says.
Gurcharan Das, who used to run the Indian operations of consumer goods group Procter & Gamble, says young members of the Indian middle class are offended by brazen displays of nepotism and aware of the dangers of employing the unqualified.