TOKYO, July 21 (Reuters) - Japanese Prime Minister Shinzo Abe's Liberal Democratic Party and its junior coalition partner, the Komeito party, look set to retain a solid majority in parliament's upper house in Sunday's election, media surveys show.
Up in the air, however, is whether the ruling bloc, along with the smaller Japan Innovation Party and independents, will keep the two-thirds majority necessary for Abe to have a chance of achieving his goal of revising the pacifist constitution.
Below are key facts about the upper house election and important numbers to watch.
WHAT IS THE UPPER HOUSE?
The upper house is the less powerful of parliament's two chambers. It lacks the authority to select a prime minister, and budgets and treaties can be enacted without its approval.
But the chamber can reject other bills approved by the lower house, and the legislation can then only be enacted by a two-thirds majority of the lower chamber. Abe's ruling bloc holds a two-thirds majority in the lower chamber.
The number of upper house seats will increase by three to 245 after Sunday's election, when 124 of the seats will be up for grabs. The total number of seats will be raised by another three to 248 in three years, when the next upper house election is held.
HOW THE ELECTION WORKS
Of the 124 seats at stake, 74 are for prefectural or provincial constituencies, each with one to six seats, where candidates with the most votes win. Another 50 seats are from a nationwide proportional representation bloc, where voters choose either a candidate or a party, and seats are allotted based on the total number of votes cast for parties and their candidates.
FIFTY-THREE, SIXTY-THREE, EIGHTY-FIVE
Abe's ruling bloc holds 70 seats that are not up for re-election, and therefore needs to win 53 of the 124 seats being contested to maintain a majority, his stated target.
The Liberal Democratic Party (LDP) and the Komeito party need to obtain a combined 63 seats to win more than half of the seats in contention and tighten their grip on power.
The ruling bloc, coupled with the Japan Innovation Party and independents who are open to constitutional revision, hold 79 uncontested seats, and need to take 85 seats on Sunday to keep a two-thirds majority, according to media calculations.
A constitutional revision requires approval by two thirds of both chambers of parliament and a majority in a public referendum. The pro-revision camp holds a two-thirds majority in the lower house. (Reporting by Kiyoshi Takenaka Editing by Robert Birsel)
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