The 45-year-old Kejriwal brandishes his party's election symbol, the broom, and in a recent election appearance he promised to "sweep out the rubbish that has accumulated over the decades."
The Congress party's Sheila Dikshit, 76, had been Delhi's top elected official, or chief minister, since 1998. Her three consecutive terms have seen the city burgeon into a megapolis of nearly 17 million people, many of them impoverished migrants in search of jobs.
Dikshit, one of the Congress party's more charismatic leaders, is seeking a fourth term as chief minister, touting Delhi's shiny new metro, numerous overpasses to ease the city's daily gridlock and the introduction of compressed natural gas-run public transport buses that have lightened the dense smog engulfing the city.
Dikshit is confident that her government's performance will again draw voters. She dismissed all talk of an anti-incumbency wave against her and the Congress.
"People can see the development work we have done. That is what will make them vote for us," Dikshit told reporters last week.
But Dikshit will have to overcome the battered image of the Congress, which over the past few years has been hit by a slew of corruption scandals, adding to public anger over its failure to push through much-needed economic reforms to revive a slowing economy.
Analysts say that the country's slow economic growth, coupled with rampant inflation of food, fuel and utility prices, have turned the middle class and the poor against the party.
"The primary issue in Delhi is price rise," said Arati Jerath, a political analyst.
"There's been runaway inflation for four years at least. Delhi is one of the most expensive cities in terms of food, accommodation, transportation and so on, whatever the politicians may say," she said.
Dikshit's main rival, the BJP's Harsh Vardhan, is a 58-year-old surgeon. A BJP loyalist, Vardhan is a former Delhi health minister.
He holds Dikshit responsible for the woes that assail the city and says his fight will be to restore Delhi to its former glory as a center of art and culture.
"She has failed on every front," Vardhan told journalists covering his campaign, listing the problems facing the city. "There is an acute shortage of paramedical staff, a shortage of essential drugs at hospitals, power and water scarcity, inflation, scams, corruption. Thousands of posts for teachers are lying vacant in government-run schools," Vardhan said.
Kejriwal hopes to take advantage of the rivalry between the main parties. But despite his fighting words, it remains to be seen whether his upstart party can make any real gains. Counting for Delhi and four other states that have also held elections this month was scheduled to be held Sunday, with the results to be declared later that evening.
Kejriwal's critics question the credibility of his party, which calls for fighting corruption and setting new standards of honesty in public life. But in an embarrassing scandal, nine of the party's election candidates were recently caught accepting money in a media sting operation.
Still, days before the poll, Aam Aadmi clearly had the two major parties concerned. On Monday, when the election campaign officially ended, both Congress and BJP warned voters against supporting the upstarts who could eat into their vote base.
"Voting for the Aam Aadmi Party is a waste of your vote," warned BJP senior leader Sushma Swaraj.
Kejriwal, however, remained confident that the people of Delhi were ready to shun the mainstream parties.
"This is not Kejriwal's fight. This is a war being fought by the people of Delhi," Kejriwal said. "And they will have the final word."
