Voters in Japan's capital go to the polls on Sunday with a candidate backed by the ruling party likely to win the race to become governor, frustrating rivals' efforts to make the vote a referendum on the prime minister's pro-nuclear energy policy.
Media surveys have shown a former health minister, Yoichi Masuzoe, backed by ruling Liberal Democratic Party (LDP), far ahead of ex-prime minister Morihiro Hosokawa, who has made opposition to nuclear power the top of his platform.
A Masuzoe victory would be a relief for Prime Minister Shinzo Abe, who suffered a rare setback last month when an LDP-backed candidate lost an election for mayor of the city of Nago on Okinawa island to the incumbent, who opposes a government plan to move a U.S. Marines' air base to his city.
Masuzoe, 65, has campaigned on promises to improve social welfare in the capital city of 13.3 million people and to ensure the success of the 2020 Olympics, which Tokyo will host.
He has not made energy policy a prime focus although he has said Japan should reduce its dependence on nuclear power in the medium- to long-term.
Nuclear energy has become contentious in Japan since the March 2011 disaster at the Fukushima nuclear power plant north of Tokyo, triggered by an earthquake and tsunami. It was the world's worst nuclear accident since Chernobyl in 1986.
Surveys have shown that most Japanese voters favour abandoning nuclear power, either immediately or in the longer term, but they also indicate that energy policy is not as important an issue for voters as jobs and the economy, an ageing population and welfare.
A win for Masuzoe, however, is not likely to mean smooth sailing for Abe's efforts to restart reactors, which were shut down after the Fukushima accident, given delays in safety checks by a new atomic regulator and the need to persuade host communities to agree to the plans.
Hosokawa, 76, who is running with support from charismatic former premier Junichiro Koizumi, opposes Abe's plans to make nuclear power a core source of energy and to restart the reactors.
Some anti-nuclear activists had urged Hosokawa and another anti-nuclear power candidate, lawyer Kenji Utsunomiya, who is backed by the Japanese Communist Party, to join forces to avoid splitting the anti-nuclear vote.
Hosokawa led an anti-LDP coalition that briefly ousted the long-ruling party in 1993 for the first time in nearly four decades, but he quit the next year over a financial scandal.
Koizumi, 72, was one of Japan's most popular leaders during his 2001-2006 term and was once Abe's mentor.
Both ex-premiers supported nuclear power while they were in office but changed their stance after the Fukushima disaster.
Among the 16 candidates is former air force chief of staff Toshio Tamogami, who resigned in 2008 after denying in an essay that Japan was the aggressor in World War Two. The pro-nuclear power Tamogami heads the nationalist group "Gambare Nippon!" ("Stand Firm! Japan").
The election is being held to replace Naoki Inose, who resigned in December over a financial scandal.