Sweden's far-right anti-European Union party is poised to make big gains in the country's general election on Sunday, capitalizing on voter discontent over issues such as immigration, crime and health care. Voters in Sweden will head to the polls to elect a new parliament and government to succeed the Social Democrat-Green coalition that has run the country for the past four years. CNBC takes a look at all you need to know ahead of the election.

Why does this vote matter?

The latest opinion polls suggest that Sweden's main center-left and center-right political blocs are practically running neck-and-neck ahead of the vote. Yet, while the governing center-left bloc is set to secure slightly more votes than the four-party Alliance bloc, both groups are likely to fall well short of a majority. The center-left had 40.2 percent of the vote, and the Alliance 38.9 percent, according to a poll by Novus late last month.

A woman walks next to election posters of the leader of the Social Democrats and Swedish Prime Minister Stefan Loefven, Swedish Minister for Finance Magdalena Andersson (L) and Sweden's Foreign Minister Margot Wallstrom on September 1, 2018 in Stockholm. JONATHAN NACKSTRAND | AFP | Getty Images

Minority governments are not usual in Stockholm, but traditional parties are struggling to attract enough voters for one overarching reason: Sweden's Democrats. Having led some opinion polls earlier in the summer, the unaligned right-wing populist party is now expected to win around 20 percent of the vote. After Italy's election of a populist government in March, the performance of Sweden's Democrats is likely to be closely monitored all over Europe.

What are the key issues?

Once again, immigration has been propelled to the top of the political agenda for another European vote. "Sweden has experienced, by far, the largest per capita immigration in Europe over the past few decades, which makes migrant-related issues especially divisive," Hakan Frisen, head of economic forecasting at SEB, said in a research note. After the Scandinavian country received around 163,000 asylum seekers in 2015, the current center-left coalition radically tightened asylum laws. But Sweden's Democrats — a nationalist party with roots in the country's white supremacy movement — has continually attacked the administration for putting the generous welfare state at risk. "Although a large majority of both the general public and members of parliament now believe that the tightening of refugee policy implemented in late 2015 should be made permanent, many difficult questions remain, particularly with political tensions connected to strains on the schools, health care, social services system and housing supply," Frisen said.

People are pictured next to an election poster of Ebba Busch Thor, leader of the Christian Democrats Party in Sweden on September 1, 2018 in Stockholm. The general elections in Sweden will take place on September 9, 2018. Jonathan NACKSTRAND | AFP

In addition to immigration, violent crime is also a key issue. It follows a string of shootings and grenade attacks in recent months. On August 13, masked men set alight up to 80 cars in Gothenburg and other towns on Sweden's west coast, in what the police said appeared to be a series of coordinated attacks. In response to the arson attacks, Prime Minister Stefan Lovren told Swedish radio: "I am really furious, what the hell are they up to?" "Society will always act hard against this and we must continue to do so… We will do what needs to be done to take care of it and go in hard against this crime," he added. Another electoral issue, which has had minimal support among voters, is a so-called "Swexit" vote. Sweden's Democrats have said they would seek to hold a referendum over whether the country should join Britain and leave the EU. Carl Bildt, the country's former prime minister, described the prospect of a "Swexit" referendum as "the biggest single danger to Sweden's future prosperity." Sweden's robust economic performance over the past few years has barely featured in this political campaign.

How does the parliamentary vote work?

The 349 lawmakers of Sweden's Riksdag are elected through a process of proportional representation. The vote will see 310 members of its parliament elected in 29 constituencies, with the remaining 39 divided up so each party's parliamentary representation is matched by the share of the national vote.

Who is likely to win?