Former Prime Minister Shinzo Abe clenches his fist after winning the party leader election of Japan's Liberal Democratic Party in Tokyo on Sept. 26, 2012. Abe, known as a hawk and nationalist, won the election to become president of the main opposition Liberal Democratic Party. (Itsuo Inouye/AP)

Poised to soon reclaim power, Japan’s main opposition party on Wednesday elected as its leader a failed former prime minister whose strong nationalist bent appears likely to strain already-damaged relations with neighboring China and South Korea.

With his selection as the Liberal Democratic Party (LDP) president, Shinzo Abe, 58, is now the odds-on favorite to become Japan’s next prime minister as the country grapples with a flagging economy and several intense territorial disputes. If the LDP, ousted three years ago, returns to power in upcoming parliamentary elections, as polls indicate it will, Abe by default will get his second shot at the premiership.

Abe’s political revival is an unlikely one, analysts in Tokyo say, because his first turn in office — 366 days, from 2006 to 2007 — was such a fiasco, dominated by cabinet scandals and ending with his resignation because of bowel problems.

But his selection also jibes with a growing concern here that Japan is under threat — a sentiment fueled by China’s maritime expansion and its aggressive claims to remote islands that Tokyo considers its own. Abe favors revising key passages in the pacifist constitution, giving more power to the Japanese military, known as the Self-Defense Forces, and allowing it to help allies if they come under attack, something it now cannot do.

In recent weeks, all five candidates for the LDP presidency had taken a get-tough-on-China position, but Abe was the most belligerent. During a candidates debate last week, he said the disputed islands are “undoubtedly, unambiguously” Japanese territory that should be protected in an “ever-forthright manner.” Beijing, Abe added, “should not enjoy membership in international society” if its government cannot keep protesters from damaging Japanese companies based in China.

Abe — the son of a foreign minister and the grandson of a prime minister — defeated former defense minister Shigeru Ishiba, 108 to 89, in a runoff Wednesday after no candidate won a majority in the first round. Some analysts say the ongoing territorial row with Beijing pushed lawmakers to support the most hawkish candidate.

During Abe’s first stint in office, Japan wasn’t nearly as concerned about nationalist issues — but he pursued them anyway. He riled other nations in the region by denying that Japan’s World War II military had forced women to serve as front-line sex slaves for soldiers. He also pushed for school textbooks to play down Japanese wartime aggression.

At the time, Abe’s strident nationalism backfired even in Japan, where polls showed more public concern about welfare programs and the limping economy. Local party members criticized Abe for being tone-deaf to the nation’s problems.

Abe’s tenure set off a widespread disenchantment with the LDP, which culminated in 2009 when the party was soundly defeated in a lower-house election, ending its 54 years of near-uninterrupted rule. Since then, the LDP has done little to rehabilitate its image as a monolithic party that spent wastefully on public works and made its decisions behind closed doors.

But the governing Democratic Party of Japan (DPJ) has done plenty of damage to its own image, with a series of abandoned populist policies and a much-criticized response to the 2011 natural and nuclear disasters. According to a Kyodo news agency poll last month, the LDP has a support rate of 21 percent, compared with the DPJ’s 11 percent, and pundits joke that the next lower-house election has become a race to see which party is less loathed.

The current prime minister, Yoshihiko Noda, has won praise during his year in office from experts and officials in Washington for his ability to win opposition party cooperation in passing a recent consumption tax hike. But the tax increase, along with Noda’s controversial push to restart a pair of idled nuclear reactors, has eroded his support among the public.

“The people’s sentiment is that the DPJ is no good, so let’s go for the LDP,” said Jun Iio, a political science professor at the National Graduate Institute for Policy Studies in Tokyo.“The problem is that . . . the LDP’s popularity is actually small. This is because the LDP has not been successful in giving an impression that they have changed.”

The LDP’s selection of Abe could yet drive support back to Noda, experts say. In particular, he must contend with sustained public opposition to nuclear power. Abe, whose party long backed the nuclear industry, has voiced concern about a government target to phase out atomic power over the next three decades.

By law, Noda doesn’t have to call an election until August, but he has indicated that he might do so as soon as year’s end. Analysts suggest that he might agree to dissolve the lower house as part of a deal to win opposition support for a key fiscal bill.

No matter which party emerges with the most seats, none is likely to have a majority, setting off a scramble to form a coalition.

Yuki Oda contributed to this report.