Japanese voters are braving strong winds and heavy rain brought by Typhoon Lan as they head to the polls in a snap general election, a year ahead of schedule.

Prime Minister Shinzo Abe dissolved the lower house of parliament and called for fresh polls last month to renew his mandate to cope with a "national crisis" amid nuclear tensions with North Korea.

A low voter turnout is expected on Sunday in the country's 48th parliamentary elections.

Following a short stint as prime minister in 2006, Abe has been in power since December 2012.

Al Jazeera looks at some of the key questions surrounding the vote.

Why were early elections called?

Many voters, as well as the opposition, have questioned the timing of the elections, particularly as Abe and his government face two corruption scandals, including allegations of cronyism.

The leader has repeatedly denied personal involvement.

Opposition parties have criticised Abe for using the vote as a way to detract from the controversy.

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Analysts say the prime minister is also looking to take advantage of a recent surge in his approval ratings due to his handling of the North Korea crisis, while "catching an unprepared, divided opposition by surprise".

"It's actually quite strange because Mr Abe already had a two-thirds majority in both houses of parliament but because his cabinet support level started to fall down quite sharply in early summer, he thought that he should seize the opportunity with the North Korea threats and the rising tensions," Koichi Nakano, political scientist at Sophia University in Tokyo, told Al Jazeera by phone.

"When his support levels started to pick up a little bit again, he wanted to attack the opposition when they were not prepared," he added.

Others say the polls come as a calculated move by the government in light of the North Korean threat.

"The prime minister had to call an election by next year anyway and probably if he waited longer, the North Korean issue may have heated up later," said Tomohito Shinoda, political expert at the International University of Japan in Minamiuonuma.

"So it's better for the Japanese government to have an election this time rather than later."

Who are the main contenders?

A total of 1,180 candidates are running for the lower house of parliament.

The elections will pit Abe's conservative Liberal Democratic Party (LDP) and its ruling coalition partner, Komeito - a Buddhist party - against the newly formed Party of Hope.

Tokyo governor Yuriko Koike launched the reformist-conservative party last month in a bid to steer voters away from the ruling LDP.

Koike, a former member of LDP, is not running as a candidate herself.

Meanwhile, the former opposition liberal Democratic Party has been weakened and divided by the emergence of two new political entities, including the Party of Hope.

The Constitutional Democratic Party of Japan (CDPJ) - another newcomer - was formed this month by former chief cabinet secretary Yukio Edano and other liberal defectors from the Democratic Party.

What are the key issues?

The nuclear threat from North Korea will be on the back of many voters' minds, but there are other pressing national issues at play.

The country's stagnant economy and social security top voter concerns, according to the polls.

Japan's once world-beating economy has not grown in years, with governments consistently failing to battle persistent deflation.

The Asian nation has one of the world's largest public debt at over 250 percent of the GDP.

"The Japanese citizens are very concerned about the direction of Japan's economy and this is related in part to its demographic issues," Stephen Nagy, expert on Japan at the International Christian University in Tokyo, said.

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Abe's brand of "Abenomics" aimed at reviving the economy has drawn criticism over the years.

Analysts say Abe's policies have benefited big companies, like Honda and Toyota, and aided urban development, but the rural areas are struggling economically.

"After Abe receives a strong mandate, he will push more for structural reform and push more on his Abenomics to get that economic growth that is happening in cities push to the rural countryside," Nagy told Al Jazeera via Skype.

Japan also has a rapidly ageing, shrinking population of 127 million, which is projected to plummet to 88 million by 2065.

The debate over the country's pacifist constitution dominated the election campaign.

The ruling LDP and the new Party of Hope are looking to revise the country's Article 9 charter, also known as the "peace clause" to clarify the legal status of the country's Self-Defense Forces.

On the other hand, LDP's junior coalition partner, Komeito, has a more cautious approach, and the new left-leaning CDPJ opposes a constitutional revision.

Nagy said the biggest challenge for CDPJ's Edano is to create a realistic security policy that can fit alongside the "principle constitutionalism" that he is supporting.

"Only the LDP has a practical and a strong record of security that can help Japan deal with some of its regional security issues, such as North Korea," he said.

Who is expected to win?

Pre-election polls and surveys in Japan forecast a landslide victory for Abe's ruling coalition, which would allow it to maintain its two-thirds majority needed to propose constitutional amendments.

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Abe's Liberal Democratic Party (LDP) and its junior partner, Komeito, are predicted to win more than 300 of the 456 seats together in the parliament, polls showed in the lead up to the vote.

"Several opinion polls suggest the ruling coalition is on track to retain its majority, but those same surveys also say many voters are still undecided," said Al Jazeera's Florence Looi, reporting from the Japanese capital, Tokyo.

Meanwhile, analysts believe that the break-up of the Democratic Party, which was the biggest opposition force, has created uncertainty among voters and will benefit Abe.

"The voters are very confused about the political landscape," said Nakano. "The new parties are doing well, but time is too limited for them to make great gains."

How do the elections work?

The general elections to the House of Representatives take place every four years, unless the lower house is dissolved earlier.

A revised electoral law that took effect in July, has reduced the number of lower house seats from 475 to 465.

Eligible voters aged 18 and above will cast two ballots - one for an individual candidate in a single-seat district and another for a political party for proportional representation.

Out of the 465 seats, 289 are elected from single-seat districts and the remaining 176 through proportional representation in 11 regional blocks.

A simple majority of above 50 percent - a minimum of 233 seats - is needed to govern.

What do the elections mean for the North Korea crisis?

The snap elections come at a time of escalating nuclear tensions and heated war of words between North Korea and Japan.

Last month, North Korea fired a ballistic missile from its capital Pyongyang that flew over northern Japan.

The test followed new UN Security Council sanctions drafted by the US.

Abe, who has maintained a hard line on North Korea, is seeking endorsement for his stance with the elections.

"Given a fresh mandate, Mr Abe will probably say that his rather hawkish stance on North Korea was vindicated," said Nakano.

US President Donald Trump is expected to visit Japan in early November and there are growing fears that the possibility of a military conflict might be considered.

"The elections will give Prime Minister Abe better control over handling the North Korean issues to prepare a deepening alliance with the US and Japan would probably strengthen its anti-missile capability," said Shinoda.

Meanwhile, Jeff Kingston, director of Asian studies at Temple University in Tokyo, said that recent NHK polls show that many voters actually disagree with Abe's policy of no dialogue with Pyongyang.

"The polls reflect concerns that his hardline position is risky and shortchanges diplomacy," he said.

Follow Saba Aziz on Twitter: @saba_aziz