The rapid pace at which four ministers of state have been promoted to senior ministers of state is a sign that they are being groomed for ministerial appointments, political observers said.
The quartet are Dr Lam Pin Min, Dr Janil Puthucheary, Dr Koh Poh Koon and Mr Chee Hong Tat.
Their move up the ranks of political leadership from May 1 was announced by the Prime Minister's Office yesterday.
Dr Lam, who will be Senior Minister of State for Health, will take on the additional portfolio of Senior Minister of State for Transport.
The other three men, who juggle two portfolios each, will stay at their current ministries.
Dr Lam, 47, was the first of the four to enter politics in 2006 and was a backbencher until he was appointed Minister of State in 2014, while Dr Janil, 44, entered politics in 2011 and took office last year.
Dr Koh, 45, and Mr Chee, 43, were elected in 2015.
The rate at which all four have moved up the ranks is noteworthy, said observers. ISEAS - Yusof Ishak Institute fellow Norshahril Saat said: "They have been seen as high fliers. Their promotion reflects their performance in the last few years."
Singapore Management University law don Eugene Tan cited Dr Janil, Dr Koh and Mr Chee - who in the space of 18 months or so rose from being minister of state to senior minister of state - and said: "They obviously have shown themselves to be equal to the task."
"Their trajectories are rather steep. Certainly, the assessment is that they are being groomed for bigger things," he added.
"The promotions, coming swiftly, reflect the pressing need to ramp up the renewal as the leadership handover draws closer.
"They will be taking on bigger challenges. For now, they are assessed to be able to be part of the core team in the 4G (fourth-generation) leadership."
The speed at which politicians are given ministry portfolios is generally seen as an indicator of their potential. Dr Koh and Mr Chee, who were elected to Parliament in 2015, went from being MPs to senior ministers of state in about 20 months.
Mr Chee, previously second permanent secretary at the Ministry of Trade and Industry, had resigned from the civil service less than a month before the September 2015 General Election.
Barely a month after he was elected that year, he was appointed Minister of State for Communications and Information, as well as Health in October.
The appointment of Dr Koh as Minister of State for Trade and Industry as well as National Development came about three months later, in January last year. The colorectal surgeon made a bid to enter politics in 2013, but was defeated in the Punggol East by-election.
As for Dr Janil, he was appointed Minister of State for Education as well as Communications and Information in January last year. The former paediatrician, however, entered politics in 2011 and spent a term as a backbencher. Associate Professor Tan noted that he "has made strides since he became an office holder".
Political observers added that the appointment of four new senior ministers of state sets the groundwork for significant changes to the Cabinet in the coming years.
They indicate that Prime Minister Lee Hsien Loong and his ministers are nurturing a larger pool of talent to consider for Cabinet positions and this points to the impending retirement of some senior ministers before the next general election, said Dr Norshahril. The election is due by April 2021.
These positions are valuable training ground, and are an important avenue allowing politicians to be groomed for ministerial positions and to prove themselves worthy of such roles, said observers.
As Institute of Policy Studies deputy director Gillian Koh pointed out, the new Cabinet appointments and other promotions show that "there's a lot of talent being nurtured right now".
National University of Singapore sociologist Tan Ern Ser said of the four new senior ministers of state: "They are probably future ministers in waiting, while being exposed to different ministries and under assessment."