SINGAPORE -- Until last month, Singapore's leadership succession plan had seemed clear. Sooner or later, Heng Swee Keat would take the reins from Prime Minister Lee Hsien Loong.
But Heng -- the finance minister, deputy prime minister and leader of the city-state's "fourth generation" team of politicians -- suddenly announced that he was taking himself out of the running.
This raised an obvious question: Who's next?
The answer remains anyone's guess, even after Lee's recent announcement of a new cabinet lineup. A handful of names from the ruling People's Action Party have been tipped as potential candidates, however, with most of the attention centering on cabinet ministers Lawrence Wong, Ong Ye Kung and Chan Chun Sing.
All are well below age 60, meaning they would meet Heng's suggested criteria for the next leader -- that he or she be someone younger than himself.
Lee, who is 69, had previously said he did not want to run the country into his 70s. But he has vowed to stay on to guide the city-state through the COVID-19 pandemic. Heng, in his letter bowing out from contention, said he feared he would be in his mid-60s by the time the crisis is over.
"The pandemic has rudely upended the best-laid plans for succession that Singapore has become known for," Eugene Tan, associate professor of law at Singapore Management University, told Nikkei Asia shortly after Heng's announcement.
Here are three people to know as Singapore searches for someone to lead its "4G team" and the city-state itself.
Lawrence Wong: Is the new finance minister the main man to watch?
The man chosen to inherit Heng's finance portfolio is seen by some pundits as the front-runner to become the country's fourth prime minister, following in the footsteps of Lee, Goh Chok Tong and Lee's father, Lee Kuan Yew.
Wong, the former head of Singapore's Energy Market Authority and the outgoing education minister, was elected to parliament in 2011 and has also served as Lee Hsien Loong's principal private secretary. He will become finance minister on May 15, when the cabinet reshuffle takes effect.
Though the 48-year-old was already second minister for finance, some observers see his selection to lead the ministry as a sign he is set to fill Lee's shoes.
"After obtaining the finance minister portfolio, Lawrence Wong has the most comprehensive ministerial experience among all 4G ministers," Yu Liuqing, country analyst for the Economist Intelligence Unit, told Nikkei.
As finance minister, Wong will take responsibility for one of two major platforms by which the government addresses Singaporeans on policy matters -- the unveiling of the annual budget. The other platform, the National Day Rally around the time Singapore marks its independence in August, is led by Lee.
Wong's role in Singapore's response to COVID-19 is widely seen as another factor in his favor.
He has been co-chairing a multi-ministry task force specially set up to tackle the pandemic. And his media briefings have made him a visible figure in the largely successful containment effort.
Wong is the youngest of the three politicians seen as having the best shot to become prime minister. Yet he has had a longer career as an elected parliamentarian than his colleague Ong. And unlike Ong, he has never lost an election race.
With opposition politicians making gains, most recently in last year's general election, the PAP is likely to be looking for a proven winner with broad public support to help maintain its uninterrupted run in power.
Ong Ye Kung: Better late than never for the incoming health minister?
Ong lost the 2011 election that put Wong in the legislature, as the opposition Workers' Party made what were then unprecedented inroads.
After his defeat, Ong opted for a private-sector role as a director at conglomerate Keppel, in which state investor Temasek holds a stake.
The political itch returned and Ong was elected in 2015, taking on the education portfolio before becoming transport minister. He will give up the transport post to become health minister on May 15.
At 51, he has the least experience as a cabinet minister, compared with Wong and Chan.
But Ong is taking over a ministry that is likely to raise his public profile, especially amid a pandemic. As health minister, he will lead the multi-ministry task force alongside Wong, making him a fixture at the briefings as well.
On the other hand, Ong's stint as transport minister following last year's general election was not entirely smooth. In October, Singapore's train network suffered an outage that lasted for a few hours and affected more than 100,000 commuters, angering some pockets of the public.
"Letting Mr. Ong co-chair the multi-ministry task force will help [him] gain more favorable publicity, after some moderate backlash against him when the city's mass rapid transit system broke down," the EIU's Yu suggested.
Chan Chun Sing: Next education minister faces hazy prospects
In theory, Chan ranks second after Heng among the 4G politicians, since the hitherto prime minister-in-waiting picked him to be his deputy. He is also second assistant secretary-general of the PAP.
Like Wong, Chan was elected in 2011 and has not lost a race. He was also entrusted with the central electoral constituency of Tanjong Pagar, once the stronghold of late founding father Lee Kuan Yew -- bolstering the perception of Chan as a possible future prime minister.
Following the 2011 polls, Chan was made a full minister before Wong and Ong. He will be shifting from trade and industry minister to education minister on May 15.
The 51-year-old was also a career soldier, rising to two-star general. Despite these credentials, however, he has taken several hits to his public image.
After the COVID-19 threat emerged last year, Chan met with members of the Chinese business community in Singapore for a closed-door discussion. In leaked audio recordings that caused a stir, Chan was heard commenting on Hong Kong's management of the outbreak, highlighting the challenge the Chinese territory faced due to diminishing supplies of masks for medical staff.
He criticized members of Singapore's public who rushed to buy essentials at supermarkets -- remarks that did not go over well with many.
After Heng stepped aside last month, dueling petitions about Chan surfaced on the website change.org -- making the case for and against him as a candidate for prime minister.
As of early May, the petition "Say NO to Chan Chun Sing for PM!" had gathered more than 7,000 signatures. The petition supporting him -- "Say YES to Chan Chun Sing for PM!" -- had mustered over 1,000 supporters.
"Chan is gaffe-prone," country risk and industry research provider Fitch Solutions noted in a report published last month following Heng's shock announcement.
The report took a dim view of his chances of taking over for Lee.
"If chosen, he will likely become an even bigger handicap for the PAP, especially during elections, due to his seeming unpopularity among the electorate, and this is the key reason why we refrain from a clear call for him to be the next prime minister."