By Tim Kelly and Kiyoshi Takenaka
TOKYO (Reuters) - Election campaigning began in earnest in Japan on Tuesday with conservative Prime Minister Shinzo Abe aiming to shake off suspected cronyism scandals and repulse the challenge from an upstart new party to extend his near-five year hold on power.
The Oct. 22 election pits Abe's Liberal Democratic Party-led coalition against the less than one-month-old Party of Hope headed by popular Tokyo Governor Yuriko Koike, a former LDP lawmaker often floated as a possible first female Japanese premier.
Calling for a snap election, Abe had said he needed to renew his mandate to cope with a "national crisis" stemming from rising regional tensions over North Korea's nuclear and missile programs and the demographic time-bomb of Japan's fast-ageing, shrinking population.
Opposition disarray and an uptick in his own ratings, which had rebounded after sinking due to a series of scandals, had encouraged the 63-year-old Abe to take the plunge.
But, the sudden emergence of Koike's party, which also appeals to conservative voters, could upset Abe's calculation. The main opposition Democratic Party imploded last month and a big chunk of its candidates are running on the Party of Hope ticket. Others created a small, liberal party.
In his first official campaign speech, Abe attacked the opposition for creating new parties and wooing voters with populist slogans.
"What creates our future is not a boom or slogan. It is policy that creates our future," Abe said in Fukushima, northeast Japan. "We just cannot afford to lose."
The LDP-led coalition had a two-thirds "super majority" of seats in parliament's lower house before dissolution, so losing its simple majority would be a major upset.
Recent opinion polls show the LDP in the lead and some analysts think Abe could even repeat his past landslide victories, since Koike appears to be losing momentum.
A soggy performance for the LDP, however, could prompt calls from inside the party to replace Abe or deny him a third term as LDP leader when his tenure ends in September 2018.
If he did secure that third term, Abe would be in a strong position to become Japan's longest-serving premier.
SHORTAGE OF HOPE?
Koike, who defied the LDP last year to run successfully for governor, calls her fledgling party a "reformist, conservative" group and is pledging to break free from the fetters of vested interests -- an often popular campaign slogan in Japan.
"We have a surplus of things in this country, but what we don't have is hope for the future," said Koike, 65, kicking off her campaign in Tokyo.
Koike has repeatedly said she won't run for a seat this time so would not be eligible for the premiership. She has until 5:00 p.m. on Tuesday to change her mind and register as a candidate.
She has also declined to say whom her party would support for premier when parliament convenes after the election, leaving the door open to a variety of possible tie-ups including with Abe's LDP.
The Party of Hope echoes Abe's LDP on security and diplomacy - it backs tough sanctions on North Korea and controversial security legislation enacted in 2015 to expand the military's role overseas.
Koike also agrees with Abe that the post-war, U.S.-drafted, pacifist constitution should be amended, though they are not necessarily agreed on what changes are needed.
On economic policies, Koike's party has sought to differentiate itself by calling for an end to nuclear power by 2030 and a freeze on a sales tax hike planned for 2019.
Abe's government wants to keep nuclear power as a key part of Japan's energy mix and raise the sales tax but spend more of the revenues on education and child care.
A center-left Constitutional Democratic Party of Japan, formed from the rump of the failed Democratic Party, aims to get support from voters satisfied with neither conservative option.
Abe's LDP had 288 seats in the lower house before it was dissolved for the election, while its junior partner the Komeito had 35. The total number of seats has been cut to 465 from 475.
(Writing by Linda Sieg; Editing by Simon Cameron-Moore)