Japan PM heads for election victory amid policy concerns TOKYO (Reuters) - Prime Minister Shinzo Abe's ruling bloc looks set for a handsome upper house election win on Sunday, cementing his grip on power and setting the stage for Japan's first stable government since the charismatic Junichiro Koizumi left office in 2006. The victory would give the hawkish leader a stronger mandate for his recipe to revive the economy and spell his personal political redemption after he led his party to a defeat in a 2007 upper house election. That poll allowed the opposition to block legislation and led to Abe's resignation two months later. After a string of revolving-door leaders, Abe, 58, returned to power following a big win in December's lower house poll for his Liberal Democratic Party (LDP) and coalition partner the New Komeito. He has said he will remain focused on fixing the economy with his "Abenomics" mix of hyper-easy monetary policy, fiscal spending and structural reforms. But some worry that Abe's resolve for economic reform could weaken in the face of a resurgent LDP. A landslide victory could bolster opposition to regulatory reform from LDP lawmakers with close ties to industries that would suffer from change. Abe could also shift his focus to the conservative agenda that has long been close to his heart, and concentrate on revising the post-war pacifist constitution and recasting Tokyo's wartime history with a less apologetic tone. Such a shift -- along with moves to strengthen Japan's defense posture -- would further fray ties with China and South Korea, where bitter memories of Japan's past militarism run deep. Tokyo is already engaged in tense territorial rows with Beijing and Seoul over tiny, uninhabited islands. Abe has declined to say whether he will visit Tokyo's Yasukuni Shrine for war dead, where Japanese leaders convicted by an Allied tribunal as war criminals are also honored. A visit on the August 15 anniversary of Japan's defeat in World War Two would spark outrage in the region. A Reuters poll showed Japanese firms generally want the LDP to win the election but worry that a landslide victory will allow Abe to prioritize nationalist policies at the expense of the economy, as critics charge he did during his troubled 2006-2007 term as prime minister. Voting begins at 7 a.m. (2200 GMT) and closes at 8 p.m. (1100 GMT) when media will project the outcome based on exit polls. Final results will be known late Sunday or early Monday. Media forecasts show the LDP and New Komeito are on track to win more than 70 of the 121 seats up for grabs in Sunday's poll for the 242-seat upper house. With the coalition's uncontested 59 seats, that would hand it a hefty majority, solidifying Abe's grip on power and raising the chances of a long-term Japanese leader for the first time since the reformist Koizumi's rare five-year term ended in 2006. Forecasts also show the LDP has a shot at winning an upper house majority in its own right for the first time since 1989, although analysts and politicians say the conservative, pro-business party is unlikely to dump its partner because it relies on it to help get votes. But the LDP and two smaller parties that back Abe's drive to revise Japan's pacifist constitution to legitimize the military looked likely to fall short of the two-thirds majority needed to take revisions of the charter to a public referendum. Those parties already have two-thirds of the lower house seats. Media have also forecast that the main opposition Democratic Party of Japan, which surged to power in 2009 to end more than half a century of almost non-stop LDP rule only to be ousted last year, could suffer its biggest drubbing since its founding in 1998. That would raise concerns about prospects for a competitive two-party democracy. Reporting by Linda Sieg