1. The SG50 factor
Observers had expected Singapore's Golden Jubilee to weigh heavily in the People's Action Party's (PAP) favour.
And it looks like the all-year-round SG50 festivities, with the biggest National Day Parade on Aug 9, did have a feel-good effect on voters.
But, more than that, celebrating Singapore's 50th year of independence and harking back to the country's early, more turbulent days, could also have reminded Singaporeans of just how unique their country is - a little red dot that not only existed, but also thrived against all odds.
During the nine days of campaigning, PAP leaders had attributed this exceptionalism to voters themselves, calling on Singaporeans to "keep Singapore special". In the end, it could have been a message too seductive to ignore.
2. The LKY effect
FAITH IN THE SYSTEM
I think many people can feel and associate with how Singapore has moved forward over the past 50 years, and are willing to put their stake in this Government to bring them forward for the next 50 years.
MR EUGENE CHEW, 49, travel industry manager
PATRIOTISM IN ACTION
We should see it as a tribute to the late Mr Lee and all that he has done for Singapore."
PAP MOULMEIN BRANCH VOLUNTEER VICTOR ANG, 50, self-employed
GOOD TRACK RECORD
The PAP has effectively responded to many of the complaints people had over the last decade. There has been a significant restriction on foreign immigration in recent years, a massive campaign to build BTO flats, and cooling measures have also brought down the resale prices of HDB flats by 10 per cent from the peak in 2013; and the economic record is objectively quite good... I think the electorate seems to have agreed.
SENIOR LECTURER AT UNISIM COLLEGE WALTER THESEIRA
SEEDS OF DOUBT
The AHPETC issue played into the PAP's hands and this affected the WP. The ground also shifted away from the opposition due to the saga.
DR NORSHAHRIL SAAT, fellow at the ISEAS-Yusof Ishak Institute.
LIKE A BIG AND SMALL BET
I think when they start to see such a great response to opposition rallies on the Internet, all the rah-rah about voting against the PAP, people got worried. People that sit on the fence say, better don't play-play. It's like a big and small bet. We want to make sure there's always checks and balances. Then I think, what if people start to think like me and we have more opposition in Parliament and things don't get done efficiently any more?
PUNGGOL EAST RESIDENT TAN YEE KEONG, 47, a regional sales manager
NEED TO MEET STANDARDS
Voters want more checks and balances but were not willing to have opposition for opposition's sake. They do expect opposition MPs to be of a certain minimum standard.
SINGAPORE MANAGEMENT UNIVERSITY LAW DON EUGENE TAN
GIVING PM THE SUPPORT
The PM is seeking a strong mandate and support. People are responding to that call, for him to take Singapore to the next stage of development. We worked very hard. At the national level, people vote PAP because they want that direction, they want to give PM the support.
HOLLAND-BUKIT TIMAH GRC MP LIANG ENG HWA
Economy uncertainty, global security concerns - these problems have always been there. It's just that this year, voters have opened their eyes, able to dissect further to say, OK, why didn't these things happen to us? They're asking the right questions now. I'm happy as a Singaporean that they're thinking that way because it makes me feel secure.
FORMER NOMINATED MP BEN TAN
The death of founding prime minister Lee Kuan Yew in March reminded Singaporeans of his key role in the country's progress.
While it evoked a sense of gratitude and sympathy, some pundits were unsure if it would translate into votes for his PAP.
But what is certain, though, is how the week of mourning galvanised Singaporeans, especially the silent majority, who turned up in the hundreds of thousands to pay respects outside Parliament House, at tribute sites around the country, and on the streets as his hearse passed by on the day of his funeral.
The sense of solidarity and patriotism could have swung votes the PAP's way. And the story of how he and his pioneer generation of leaders built Singapore could have driven home the importance of a good leadership, which was a key plank of the PAP's campaign this election.
3. Policy changes
The Workers' Party (WP) had campaigned on it, telling voters that the Government's policy "U-turns" over the past four years were the result of a stronger opposition presence in Parliament.
It turns out though, that voters could have given the PAP credit for the policy changes instead.
In areas such as immigration and property prices, the Government took quick, decisive actions to tighten the tap on foreigners and bring down property prices.
These policy changes have, possibly, defused a number of hot button issues that turned up the heat in the 2011 elections and given voters fewer reasons for protest.
Over the past four years, the leftward shift that the party had taken had also become more obvious, drawing praise from opposition parties and activists alike.
4. The AHPETC controversy
The issue of the WP's Aljunied-Hougang-Punggol East Town Council (AHPETC) dominated the first half of this election's campaign for both the opposition party and the PAP.
On the one side, the PAP had attacked the WP for lapses at its town council, saying it exposed a deeper integrity problem at the party.
On the other side, the WP had painted itself as a victim of the ruling party's bullying, saying the PAP was using the town council system to hobble opposition parties.
But, in the second part of its campaign, the WP had moved away from the issue, seemingly confident that voters would not care.
As it turns out, voters may not have bought the opposition party's story - that the whole issue was just being stirred up unnecessarily by the PAP.
Perhaps the surest sign of this is the party's results in Aljunied GRC, most associated with the town council issue. The party barely clung onto the constituency, polling just 50.95 per cent of valid votes.
5. Fear of the ‘what-ifs’
At the final Workers' Party (WP) rally of the campaign period, Hougang MP Png Eng Huat made a call for sweeping change.
He said a fundamental overhaul of Singapore's political landscape was needed and that it could only be realised with a wave of support for the WP. Singapore needed "big change" at the polls, he said, or "nothing else will change at all".
Those comments - taken in the context of this campaign and opposition leaders openly talking about the need for at least 20 opposition MPs - may have presented undecided voters with too much of a change all at once.
6. Quality of the opposition
While it was unlikely that anyone seriously bought into the PAP warning that it might fail to form the government, the opposition might have offered a vision of the future they were not yet ready to embrace.
While the 2011 General Election was marked by excitement over a series of "star-catches" by opposition parties, there was a comparatively muted response to this year's slate.
Part of it was simply because the voters had seen it all before. Highly qualified former government scholar with stellar academic credentials? There were four in 2011, not including WP's Chen Show Mao. Young, fresh-faced, articulate female candidate? There was National Solidarity Party's Nicole Seah.
It is unclear if these star catches made all that much difference. PM Lee's criticism that the opposition was a "mouse in the House" may have found agreement with some voters.
Opposition parties seemed less prepared for battle in 2015 than four years ago, when they presented a more thought-out strategy.
The NSP was hurt by its constant flip-flopping on its decision to contest MacPherson SMC; the Singapore People's Party and Democratic Progressive Party could not agree on a joint team until the 11th hour; and the Internet had a field day with two separate Reform Party candidates who accidentally called on voters to support other parties.
7. PM Lee's like ability
Prime Minister Lee Hsien Loong may be one of the PAP's most popular politicians, but many observers still felt that his decision to place himself at the heart of the campaign was a risk.
Posters of his smiling face were everywhere during this campaign, much to the chagrin of the opposition candidates. PM Lee also made campaign stops in various constituencies and sent e-mail to voters that was signed by him.
The results are evidence that the gamble paid off. The PAP made gains across the board and PM Lee ended up with one of the best-performing wards in the election. Voters also rewarded him with the strongest mandate of his tenure.
8. External environment
In a departure from recent years, Prime Minister Lee Hsien Loong spent a significant chunk of this year's National Day Rally talking about global issues.
"We have to be alive to our external environment, that's a fundamental reality for a 'little red dot'," he said, as he explained how instability in Singapore's neighbourhood could affect the nation.
For voters who had kept up with global affairs, they might have seen that all is not well with the world at the moment.
Even as Singapore's election campaign was picking up steam, its closest neighbour, Malaysia, was contending with growing unrest over corruption allegations involving the prime minister and China's massive stock market crash captured headlines around the world.
•Reporting by May Chen, Walter Sim, Nur Asyiqin Mohamad Salleh, Marissa Lee, Audrey Tan, Lim Yi Han and Zhaki Abdullah