SANTIAGO, Nov 18 (Reuters) - Chile is set to vote for a new president on Sunday, with a far-right conservative battling for pole position against a young former student leader on the left, in the most polarized election since the country"s return to democracy in 1990. The vote is the first presidential ballot since Chile was rocked in 2019 by months of angry protests against economic inequalities that eventually sparked a process - still ongoing - to redraft its decades-old constitution. HOW WILL THE VOTE WORK? The Nov. 21 election will see Chileans vote for a new president, members of Congress and regional councils. A presidential candidate needs over 50% of the vote to win outright, otherwise there will be a second-round head-to-head on Dec. 19.The voting starts at 8 a.m. (1100 GMT) and ballot stations close around 6 p.m., with results expected to come in fairly quickly Sunday evening. WHO IS RUNNING? There are seven presidential candidates. The two front-runners are 55-year-old ultra-right former congressman Jose Antonio Kast, leading in opinion polls ahead of Gabriel Boric, 35, a former leader student running for a leftist coalition. Behind the front two are more mainstream contenders: center-right Sebastian Sichel from the ruling coalition who is a former minister of President Sebastian Pinera, and Yasna Provoste, a senator from a mining region with the major Christian Democrat party. Experts have cautioned that opinion polls could miss the mark with the field so fragmented, opening the door for a potential surprise. But a Kast versus Boric head-to-head in December appears the most likely outcome. WHAT ARE THE MAIN ISSUES? Many Chileans support the free-market policies that propelled the copper-rich country to decades of growth and made it a bastion of relative economic stability in volatile Latin America. But an increasing number want change to address the deep inequalities. Some of the loudest demands have stemmed from anger over paltry retirement payouts blamed by critics on Chile"s highly privatized pension system, while others have criticized the high costs and sometimes dubious quality of privatized education, and gaps between public and private healthcare. Conservative voters have raised questions about increased immigration, and there are law and order concerns sparked by the protests in the capital and violent clashes between police and Mapuche indigenous groups in the country"s south. Whoever wins the presidency will also have to handle a referendum to approve or reject the text of a new constitution during their first year in office. An assembly, dominated by leftist and independent representatives, is leading the constitution redraft. "With so many problems, candidates are having to offer solutions that are drastic and that is why we have two leading candidates who are rather extreme," said Kenneth Bunker, director of political consultancy Tresquintos.