Factbox: Malaysia's Najib to face toughest election yet on Wednesday
KUALA LUMPUR (Reuters) - Malaysia's Prime Minister Najib Razak and his ruling coalition face their toughest general election on Wednesday with an unprecedented challenge from his former mentor turned opposition leader Mahathir Mohamad.
Najib is under pressure to deliver a convincing victory for his undefeated Barisan Nasional (BN) coalition, as he grapples with financial scandals and public anger over rising prices.
Najib's coalition is still expected to win the election, but a significant loss of seats to the opposition could leave the prime minister open to a leadership challenge within his United Malay National Organisation (UMNO) party.
Below is a summary of the electoral process and key facts about Malaysia:
CAMPAIGNING AND POLLING
The polling date and campaign period are decided by the Election Commission (EC). The 11-day campaign began on April 28. Polls open on May 9 at 8 a.m. (0000 GMT) and close at 5 p.m. (0900 GMT).
There are nearly 15 million registered voters. Full results are expected to be announced by midnight the next day, EC officials said.
POLLING SYSTEM
Malaysia adopted a Westminster parliamentary model after gaining independence from Britain in 1957. The government is elected through a first-past-the-post, or simple majority, system.
The UMNO-led coalition has been undefeated since independence. The coalition contains parties representing the country's three main ethnic groups: majority Malays, most of whom are Muslim, ethnic Chinese and ethnic Indians.
The opposition has accused the government of gerrymandering, rigging and propaganda through state-controlled media to secure a victory in every election. The government has denied those accusations.
Critics have also said the Election Commission favours the ruling party. The commission has repeatedly denied that.
NUMBERS GAME
The general election is for all 222 seats of parliament's lower house, known as the Dewan Rakyat.
Najib's ruling coalition won 133 seats to win the last general election, in 2013, despite losing the popular vote.
The opposition coalition is hoping it can whittle down BN's seat count to gain at least 112 seats - which would give it the right to form a government.
The 70 members of parliament's upper house, known as the Dewan Negara, are appointed, not elected.
GEOPOLITICAL HOT SPOT
Malaysia is a major exporter, its economy driven by oil and gas, palm oil, rubber and electronics.
Part of the South China Sea lies between east and west Malaysia, a maritime region that falls within an area claimed by China, and delineated by a "nine-dash-line" on its maps.
Malaysia - and several other countries in the region - have disputed China's claim over the South China Sea, through which about $5 trillion in trade passes annually.
(Reporting by Joseph Sipalan; Editing by Darren Schuettler)