TOKYO — Yoshihide Suga, Prime Minister Shinzo Abe's right-hand man, is in a strong position to succeed his boss in Japan's top job, experts said Tuesday, after key factions within the ruling party fell into line behind him.

Suga, who has a reputation as a skilled backroom operator but a less-than-charismatic public figure, appeared set to defeat a challenge from Abe’s archrival, Shigeru Ishiba, though polls show he is significantly less popular among rank-and-file party members and the general public.

Abe shocked the nation Friday by announcing his resignation because of ill health, although Japan’s longest-serving prime minister will remain in the job until a successor is found.

On Tuesday, Suga’s chances of taking over received a boost when the ruling Liberal Democratic Party (LDP) decided to exclude ordinary party members from a leadership vote Sept. 14 and allow only parliamentarians and limited representatives of prefectural chapters around the country to cast a ballot.

That effectively leaves the choice of Japan’s next prime minister in the hands of a small group of elderly male power brokers. And it’s already clear those power brokers have chosen continuity and stability ahead of popularity, with Japanese media reporting that the largest factions have backed Suga.

“This is all an effort to keep Ishiba from winning the election,” said Gerald Curtis, a political science professor at Columbia University and veteran observer of Japanese politics.

“Suga will become prime minister, and the media world and public opinion will say, ‘It’s terrible the rank and file didn’t have a voice,’ ” he said. “But I think if he plays his cards right, within a month you’ll start hearing people say: ‘Well, this guy, he’s got this covid problem under control. He’s taken steps to make the economy stronger. He’s not a charismatic figure, but he knows how to get things done.’ ”

Diplomatically, Suga would also likely follow in Abe’s footsteps, simultaneously attempting to strengthen the alliance with the United States while improving relations with China. But he is not known as a foreign policy expert and lacks Abe’s stature on the world stage.

President Trump was effusive in his praise for Abe after he announced his resignation, calling him “the greatest Prime Minister in the history of Japan.” The two had bonded over their nationalist politics and love of golf.

But Suga’s more reserved nature could prove a hurdle in building a similar relationship with the U.S. president — especially if Trump wins reelection.

“He will likely be skillful at managing the government or the party, but it is unclear how skillful he will be with diplomacy or security issues,” said Jeffrey Hornung, a political scientist at Rand Corp. “In the realm of foreign and security policy, Suga will likely continue with the same policies as Abe, but I can’t imagine Suga being the globe-trotter like Abe.”

Suga has served as chief cabinet secretary and the government’s main spokesman in the Abe administration since 2012. He also managed personnel appointments, coordinated interministerial policy and had his say within a small group of key decision-makers around the prime minister.

Effectively, he is the man who kept the ruling party and the bureaucracy in line behind Abe for more than seven years, and he is widely seen as having been effective in that role.

Abe’s popularity slipped this year over perceptions he had not done enough to tackle the twin challenges of the coronavirus pandemic and a collapsing economy.

If he wins, Suga’s first challenges will be to show he is fully in command, and to communicate more effectively with the public. But his image — as a “sober and mature Mr. Fix-it” — could be an advantage in a crisis, Curtis said.

Under normal circumstances, the LDP leader is elected in a complex ballot structure that gives equal voice to parliamentarians and rank-and-file members in a first-round vote. If no one secures a majority, the winner is determined by a narrower ballot of parliamentarians in a second round. In 2012, Ishiba beat Abe in a first round of voting but lost the second.

Some 145 LDP parliamentarians, including Ishiba, submitted a petition Monday asking for the same procedure this time around, but that appeal was rejected by party leaders, who cited the need to make a swift decision on the next leader after Abe’s shock resignation.

For Suga, winning over the public would be a vital early requirement.

“The perception that LDP factions colluded to secure his selection will make it that much harder for him to build public support for his government,” said Tobias Harris, a senior vice president at Teneo, a consulting and advisory firm.

But Harris said it was little surprise to see party leaders opting for a figure “most likely to provide administrative continuity” as the country grapples with the novel coronavirus.

Economically, Suga would be unlikely to depart much from Abe’s strategy of using fiscal and monetary stimulus to keep Japan’s economy afloat but isn’t thought likely to be any bolder in pushing through the structural reforms needed to really put wind in the economy’s sails.

Like Abe, he would resist calls to impose another state of emergency if coronavirus infections rise, instead prioritizing efforts to restart the economy, experts said.

Another of his early challenges would be managing his leadership rivals — Ishiba and former foreign minister Fumio Kishida — and other potential successors such as Defense Minister Taro Kono, as well as the party’s powerful right wing, said Harris.

Suga is expected to formally announce his candidacy at a news conference Wednesday.

The Sept. 14 election will decide on a leader to see out the rest of Abe’s term, which lasts until September 2021.