With lawyers, businessmen, former civil servants, a finance professional and a professor among the Workers' Party's (WP) slate, it is a list that may have sparked charges of elitism if the candidates were wearing white.

In the WP's blues, they are instead seen as a refreshing change as the opposition has only in recent years started to attract candidates of such calibre.

Continuing a trend that started in earnest from 2011, the WP this time unveiled a slate with more professionals, many in their 30s and 40s.

Party chief Pritam Singh has emphasised several times that the party's candidates will be good at both providing checks and balances in Parliament and also running town councils, suggesting that they will need some credentials.

All nine of the WP's new faces are graduates, and they range in age from 26 to 54.

Among them, Dr Jamus Lim, 44, with degrees from the London School of Economics, Harvard University and University of California, Santa Cruz, among other schools, has created the most buzz.

Ms Raeesah Khan, 26, a social activist who started the Reyna Movement to empower women, meanwhile, has sparked some excitement, being the daughter of one-time presidential hopeful Farid Khan.

There is also more gender and racial diversity this time in the party's slate, putting paid to the criticism before that it is a Chinese party made up mostly of old men.

It has worked hard to shed that image and of its 21 candidates for this election, five are women and seven are from a minority race.

In 2015, it had the same numbers of women and minority candidates, but a pool of 28 candidates.

No other opposition party has been able to consistently attract such quality candidates, and the WP's ability to do so in successive elections has partly contributed to its image as a serious-minded party that credible people will join.

Though this emphasis on credentials has caused unhappiness within the party's ranks, with some finding it unfair that older and more humble activists are passed over for candidacy, and others feeling that there is less diversity in terms of class, the party looks set to continue with this formula that has served it well.

For now, it has confirmed only its line-ups for Aljunied GRC and Hougang SMC.

Mr Singh has told voters that he will stand in Aljunied, along with current teammates Sylvia Lim and Faisal Manap, as well as Non-Constituency MP (NCMP) Leon Perera and former NCMP Gerald Giam, who will take the places of Mr Low Thia Khiang and Mr Chen Show Mao.

This quelled rumours of a possible move by Ms Lim to Punggol West SMC, Sengkang GRC or East Coast GRC at the last minute.

In Hougang, NCMP Dennis Tan will replace Mr Png Eng Huat.

But the party has so far not disclosed its slate for any of the other constituencies, including the new Sengkang GRC, which some have said could see one of the hottest battles.

Dr Lim, Ms Khan and equity analyst Louis Chua, 33, have all been spotted walking the ground there.

Meanwhile, the party will also be fielding Ms Nicole Seah, 33, a former National Solidarity Party candidate, who has been spotted walking the ground in East Coast.

It is anyone's guess how these new faces will contribute to the party's vote share, but at the very least, it has helped the party to solidify itself as a serious opposition party which can bring in good quality people.

As for the Progress Singapore Party (PSP), the biggest newcomer and the opposition party fielding the largest number of candidates, its slate was being watched for the age of its candidates.

This is especially given that when the party was first started last year, it was also thought of by some as an "old man party".

Its party leader, Dr Tan Cheng Bock, is still set to be the oldest candidate in the election at 80, but the party also has the youngest candidate, 23-year-old law undergraduate Choo Shaun Ming. PSP's 24 candidates ultimately turned out to be a mix of professionals across age groups.

The party also teased a possible high-profile candidate in the form of Prime Minister Lee Hsien Loong's brother, Mr Lee Hsien Yang, with the 62-year-old doing walkabouts in Tanjong Pagar GRC. The party has, however, strenuously avoided indicating whether he would contest.

Across the other opposition parties, there is a sense from the slates of candidates fielded that the election is one of consolidation rather than growth.

Other than the new parties like the PSP, Red Dot United and Peoples Voice, all other opposition parties are fielding the same number of or fewer candidates than they did in 2015, and most have slates that feature fewer new faces than they did at the past election.

The slates for the likes of Reform Party and Singapore Democratic Alliance (SDA) feature a large majority of those who had contested for the parties before. The People's Power Party (PPP) is set to field a single candidate, its party chief Goh Meng Seng.

The Singapore Democratic Party, which was among the first parties to give a strong indication of their line-ups, looks to be fielding the same team leaders for its group representation constituencies that it did in 2015.

From its likely line-up, only three have never stood for an election before: director of a food and beverage chain Alfred Tan, 54; marketing communications professional Min Cheong, 35; and entrepreneur Robin Low, 45. The party looks set to contest the same five constituencies it did in 2015.

For the Singapore People's Party, which went through a leadership renewal last year, this election also marks one of the smallest line-ups fielded by the party. Its GRC team sees long-time party members step into the candidate role.

Perhaps its most notable new face is its new party chairman Jose Raymond, 48, who works as the chief strategy officer of a communications firm.

For some like PPP's Mr Goh and SDA chairman Desmond Lim, this will be the last hurrah. Both have indicated that they will be bowing out after this general election, perhaps paving the way for more consolidation in the opposition camp in future.

• Additional reporting by Fabian Koh