By Rupam Jain and Tom Lasseter
LUCKNOW, India (Reuters) - Prime Minister Narendra Modi faces his biggest electoral test since coming to power when the battleground state of Uttar Pradesh, which he swept three years ago, holds an election starting on Saturday.
In the biggest democratic exercise on the planet this year, voting will take place in seven stages over a month to elect a new assembly to govern the mostly poor state of nearly 220 million people that lies along the river Ganges.
More broadly, voters will deliver a mid-term verdict on Modi and his nationalist party as India recovers from his boldest decision yet: to abolish 86 percent of the cash in circulation.
The banknote ban, launched by Modi three months ago to purge the economy of untaxed income and proceeds of crime and corruption, has disrupted daily life and commerce, and caused the economy to slow.
On the campaign trail, Modi has said he had the interests of the poor at heart in making the move - the biggest gamble of his prime ministership. A strong showing at the polls would strengthen his chances of a second term in 2019.
"The results will tell us whether Modi continues to enjoy unquestioned support or if it has started to erode," said R.K. Mishra, an independent political analyst based in the state capital, Lucknow.
GODZILLA OF STATES
Modi's Bharatiya Janata Party (BJP) polled 42 percent of the vote in Uttar Pradesh in the 2014 general election, sweeping 71 out of 80 seats on its way to claiming India's biggest national mandate in three decades.
Yet voters have shown growing impatience that Modi's campaign promises of development and "better days" to come have failed to deliver new jobs to a state where per capita incomes average less than $750 a year and many communities lack access to power, clean water and basic medical services.
"It is the Godzilla of states," said BJP national spokesman Nalin Kohli, as he looked out over the darkened streets of Lucknow on a recent evening.
People tend to vote along traditional caste and religious lines, and successive governments have exploited communal divisions to fire up their base and poach voters from opponents.
"The situation gets very bad here sometimes – there is fighting between groups, between Hindus and Muslims," said Bhagwati Prasad, who sells materials for Hindu cremation ceremonies outside a temple in Lucknow.
"I am a Hindu. If there is a Hindu-Muslim fight I have to stand with the Hindus."
The complexity of such "vote-bank" politics makes it hard to predict outcomes in India's first-past-the-post electoral system. Any party polling significantly over 30 percent of the vote can win by a landslide.
Pollsters say it will be tough for the BJP to repeat its general election performance.
In not fielding its own candidate for the post of chief minister it also risks repeating a tactical blunder that contributed to a heavy defeat in Bihar, another Hindi-speaking heartland state, in 2015.
The Samajwadi Party, which rules in the state, is led by 43-year-old Chief Minister Akhilesh Yadav. The party won a majority in the last state assembly election, in 2012, with just 29 percent of the vote.
Yadav has formed an alliance with Rahul Gandhi of the Congress party that, polls show, will be tough to beat.
In the third corner of the contest is Mayawati, who ran the state from 2007 to 2012 and whose Bahujan Samaj Party draws its support from communities on the bottom rung of India's ancient caste hierarchy.
She has fielded a big crop of candidates from the Muslim minority that makes up 19 percent of the state's electorate. Polls show most Muslims siding with the ruling Samajwadi Party-Congress alliance, however.
The Center for the Study of Developing Societies, a Delhi-based polling group, projects Samajwadi-Congress to win 35 percent, followed by the BJP on 29 percent and the BSP on 23 percent. Other polls put the BJP ahead.
Results from Uttar Pradesh, along with elections in the states of Punjab, Goa, Uttarakhand and Manipur, are due on March 11.
For a graphic on Map of Indian state elections, click: http://fingfx.thomsonreuters.com/gfx/rngs/1/1627/2762/INDIA-CONGRESS.jpg
For a graphic on Map of Uttar Pradesh elections, click: http://fingfx.thomsonreuters.com/gfx/rngs/INDIA-ELECTION/010031R2407/INDIA-PASTRESULT.jpg
For a graphic on Wealth, criminal charges and election success, click: http://fingfx.thomsonreuters.com/gfx/rngs/INDIA-ELECTION/010031QH3YX/INDIA-ELECTION-CANDIDATE.jpg
(Writing by Rupam Jain; Editing by Douglas Busvine and Robert Birsel)