Backgrounder: Key facts about Israeli elections

Israelis go to the polls Tuesday in an early parliamentary election, where the opposition center-left Zionist Union is posing a strong challenge to the Likud party led by Prime Minister Benjamin Netanyahu.

Here are some key facts relating to the elections:

-- A total of 24 parties are vying for the 120 seats in the single-chamber parliament, the Knesset, Israel's 20th. Largely because of mergers of several parties, there are fewer parties than the last election, but only about 12 parties are expected to get enough votes to be represented in the Knesset.

-- Knesset elections are based on the vote for a party rather than for individuals. Knesset seats are assigned in proportion to each party's percentage of the total national vote. The threshold for a party to be represented in the parliament was raised in 2014 to at least 3.25 percent of the total votes cast.

-- There are 5,881,696 eligible voters and 10,119 polling stations across the country. Election day is a holiday in order to enable all potential voters to participate. Voter turnout in 2013 election was 67.8 percent.

-- Polling stations are generally open from 7 a.m. to 10 p.m. In small towns, jails and hospitals, polling stations are open from 8 a.m. to 8 p.m.

-- National elections to the Knesset are held once every four years, unless circumstances call for early elections.

-- Every Israeli citizen 18 years of age or over is eligible to vote for one registered political party. Every Israeli citizen who is 21 years old and up may be elected. Israel had previously experimented with a direct vote for the prime minister, but has since gone back to the current electoral system.

-- After the elections, President Reuven Rivlin will hold consultations with the parties elected to the Knesset and assigns the task of forming the new government to a Knesset member. This legislator is usually the leader of a party or coalition winning the most seats in the Knesset.

-- The prime minister-designate has a period of 28 days to form a government, which can be extended by 14 days. If successful, he or she becomes prime minister; if not, the president may then assign the task to another parliamentarian.

-- When a government has been formed, the designated premier presents it to the Knesset within 45 days of publication of election results. The government is installed when the Knesset has expressed confidence in it by a majority of 61 Knesset members, and then the ministers assume office.

-- In Israel's 67-year history, no single party has received enough Knesset seats to be able to form a government by itself; thus the country has always been governed by a coalition. Endit