As the northern Indian state of Uttar Pradesh begins a seven-phase election later this week to choose a new government, the BBC's Geeta Pandey in Delhi explains why these polls matter. LUCKNOW — Over the next month, elections will be held in five Indian states, but all eyes are on the key battleground of Uttar Pradesh. Commonly known by its initials UP, the state is India's most populous, with an estimated 240 million people. If it were a separate country, UP would be the fifth-largest by population in the world, after China, India, the United States and Indonesia — and larger than Pakistan or Brazil. The state sends the largest number of MPs — 80 — to India's parliament and it is often said that the party that wins the state ends up ruling the country. Several prime ministers, including India's first PM Jawaharlal Nehru, have come from here. Prime Minister Narendra Modi, who is from the western state of Gujarat, also chose to make his parliamentary debut from the state in the 2014 general election when he stood in Varanasi. In 2019, he was re-elected from there. And voters in the state can easily claim the credit for his Bharatiya Janata Party's (BJP) sweep of the last two general elections — in 2014, the party won 71 seats here; in 2019, it got 62. Main players Since the late 1990s, state politics have been dominated by the regional Samajwadi Party and Bahujan Samaj Party (BSP). As the two alternated in power, the Congress and the BJP were pushed to the margins. But in 2017, the BJP won a thumping majority, winning 312 of the 403 state assembly seats and nearly 40% of the popular vote, riding on the popularity and charisma of PM Modi. The party chose Yogi Adityanath, a highly polarising saffron-robed Hindu monk-turned politician known for his divisive views, as the chief minister and he is hoping for an encore when the votes are counted on 10 March. Lending him a helping hand is Mr Modi who has made nearly a dozen trips to the state in recent months, addressing gatherings and exhorting voters to give the BJP another chance. In the past year though, the party has lost a lot of ground over contentious farm laws - which the government scrapped after a year of protests by farmers - and the state government's disastrous handling of the Covid-19 pandemic last year. Hundreds of bodies, believed to be of people who lost their lives to coronavirus, turned up in the Ganges river. And although the government has been appreciated for providing free rations during the pandemic, there's discontent over a lack of jobs among young people and runaway inflation. At election rallies though, Mr Adityanath, 49, has been claiming to have created plenty of jobs, boosted the economy and improved law and order in the state. He's also been using anti-Muslim rhetoric to win Hindu votes. Mr Adityanath's main challenger is the Samajwadi Party led by 48-year-old Akhilesh Yadav, a former chief minister ousted by the BJP in 2017. Mr Yadav has been working hard to wrest power from the BJP, and he's promised free electricity to all households, pensions for poor women and interest-free loans to farmers if he's voted into power. His chances have brightened after he stitched up alliances with a number of smaller regional parties. The BSP, led by Dalit (formerly Untouchables) icon Ms Mayawati, is also seeking a comeback but not many are willing to bet on her. The four-time state chief minister, who lost power in 2012, is popular among her community, but during her earlier stints she was criticised for spending millions of dollars to build statues of herself and other Dalit icons. Out of power now for a decade, she has been pushed to the sidelines and has maintained a low profile this election season. A host of smaller parties are also in the fray and so is the Congress, India's main opposition party. Led by Priyanka Gandhi, the Congress has grabbed attention with her energetic campaign. She has made news by visiting families of rape victims and police atrocities; and her focus on female voters has made headlines. Even as her personal stock remains high, her campaign is hobbled by a lack of support on the ground. What's at stake? Because of its sheer size and numbers, Uttar Pradesh is a crucial battleground. And for the parties in the fray, these elections are being seen as a do-or-die battle. No party has won a second term here since 1989, so the BJP and Mr Adityanath will be keen to break that jinx. The election result will also be seen as a referendum on his politics of Hindu nationalism. For Mr Modi too, the elections are significant as UP is seen as a test run before the 2024 general elections and if the BJP loses here, it will be seen as a sign that the pull of the party and the prime minister are on the decline. A victory for Akhilesh Yadav is crucial as another term out of power is likely to weaken his position as the leader of his party. A loss will also likely put an end to the alliances he's forged with smaller regional groups. A win is also absolutely essential for Ms Mayawati, who has spent the past 10 years in the political wilderness. Analysts say if she loses this time too, she may never be able to bounce back. The Congress, analysts say, is not really playing for a win this time, but is hoping that all the hard work put in by Priyanka Gandhi will help revive the party and help it build for a substantial role in the future. With 403 seats up for grabs, thousands of contestants are in the fray, fighting for a share of the pie. More than 150 million voters will be casting their votes at 174,351 polling centers, during the seven phases of voting spread over a month. Thousands of police and paramilitary troops are being deployed to ensure the elections are free and fair. But despite its political significance, UP remains one of India's least developed states and home to the largest numbers of poor people in the country. According to the recently-released first-ever multidimensional poverty index, 37.79% of the state's population lives in poverty, more than 44% are deprived of nutrition and millions still have no access to toilets. For the voters, the only way to express themselves is through their vote. And during elections they come out in large numbers to use it - often against those in power.