The unprecedented challenge that Workers' Party (WP) chief Low Thia Khiang faced on Sunday for the post of secretary-general from fellow Aljunied GRC MP Chen Show Mao made public the rumblings that have been going on in the party for some time.

What lies behind it, and how Mr Low responds to the first contest for the post that he has held for 15 years, will impact on how the WP continues to be regarded by its members and supporters alike.

The rumblings appear to be over leadership style, the WP's future direction and its poorer performance - by way of overall vote share - at last year's general election compared with GE2011.

There has been talk that while younger talent are being groomed, and they are getting prominent positions - whether by being fielded as general election candidates or by being co-opted into the Central Executive Council (CEC) - these are occurring at the expense of older members.

The party's showing at GE2015, where its younger and next-generation politicians were in the limelight, and where the WP narrowly retained Aljunied GRC but lost Punggol East, had some questioning the effectiveness of Mr Low's strategy.

Clearly, a number of cadres, backed by non-voting members, believed Mr Chen could bring changes, including, according to sources, being more consultative and allowing a better share of decision-making.

That Mr Low prevailed with 61 votes against Mr Chen's 45 at the biennial CEC election shows that the veteran politician still commands broad support.

Some analysts suggest that the challenge shows the WP's level of maturity: It can entertain a challenge and survive a leadership change if it came to that.

Still, the challenge was a shot across Mr Low's bows. While he retains the mandate to lead, and even Mr Chen urged members to move on together, Mr Low must address issues that concern members lest unhappiness grows. If that festers, the strains will show and the fabric of the party could split. The CEC result, in fact, allows Mr Low to show he is a leader able to unify the party, and the ball is now in his court.