Uttar Pradesh (UP) is India's largest state, accounting for around one-sixth of total population.
Elections in the state have national implications making it a crucial battleground state for political parties.
For the BJP, the elections are a test of of PM Narendra Modi's post-demonetization popularity.
For the opposition, a UP win represents a comeback ahead of the 2019 general elections.
What's at stake for parties in UP elections?
UP elections at a glance
Elections in UP will take place over seven phases from February 11 to March 3. As many as 14,12,53,172 voters are eligible to cast their ballots. The votes will be counted on March 11.
Impact on Rajya Sabha
Will aid BJP's reform agenda
In 2018, 10 out of the 68 seats up for grabs in the Rajya Sabha (RS), will come from UP.
The BJP-led National Democratic Alliance (NDA) currently has 74 seats in the RS.
A UP win for the BJP may not help it achieve the crucial 123 seats majority in the RS, but it will make its job of passing key legislation less tedious.
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Is UP India's kingmaker?
There is a common belief that the road to Delhi goes through UP. The winner of UP elections may determine who will stay in the Prime Minister's 7 Race Course Road residence in 2019.
Modi's mid-term exam
A UP win would represent a thumbs-up for demonetization and bolster PM Narendra Modi's image.
It will help Modi consolidate power and give impetus to his high-risk initiatives (such as demonetization) for the second half of his term.
CM's future uncertain
The UP assembly elections represent a make or break scenario for Chief Minister Akhilesh Yadav's political career.
He is fighting an all-out war with his father Mulayam Singh Yadav and uncle Shivpal Yadav to wrest control over the Samajwadi Party.
At stake is Akhilesh's developmental brand of politics against the Mulayam-Shivpal old guard's caste-based politics
Mayawati desperately needs a comeback
Bahujan Samaj Party (BSP) supremo former CM Mayawati lost the UP polls in 2012 to SP.
BSP was routed by the BJP in the 2014 Lok Sabha elections and failed to win even a single seat.
She is banking on dalit-Muslim votes to make a political comeback after spending five years in the sidelines.
Mayawati's loss could cause the end of her political career.
Rahul tries leading Congress's revival
Congress has been relegated to the fourth place in the UP elections and is seeking an alliance, possibly with the SP.
The party had upped the stakes in UP with Rahul Gandhi's yatra across the state.
Its much sought revival in the national stage against the BJP will depend on its performance in the UP elections.
22 Jan 2017
Cong-SP alliance announced for UP polls
After weeks of speculation, the Congress officially announced an alliance with the Samajwadi Party for the UP elections after Sonia Gandhi involved herself in the negotiations.
Though the Congress wanted to contest from 121 seats, the party will only fight from 105 seats under the alliance.
Akhilesh Yadav had earlier announced that he would not give more than 100 seats for Congress to contest.
25 Feb 2017
'Is there anyone who hasn't copied?': Akhilesh on 'nakal' remarks
After PM Narendra Modi accused the UP government of protecting the "copying mafia", CM Akhilesh Yadav said, "All of us at some point of life have indulged in copying. Is there anybody who hasn't copied in schools?"
He added the BJP had "copied our election promises".
Saying Modi's focus is on "kabristan aur shamshaan", Yadav said SP's attention was instead on "laptop and smartphone".
06 Mar 2017
UP: BJP highlights crimes against women under Akhilesh govt
BJP president Amit Shah sought to highlight the crimes against women in UP under the Akhilesh Yadav government, saying the SP "made UP the number one state in the country in terms of murder, loot and crime against women."
He was speaking at a rally in Lucknow.
He also targeted the mining districts highlighting the poor development in the economically important region.