The major issues dominating this election cycle include a stalling economy, immigration, the social safety net -- including concerns over healthcare and the retirement-savings program known as the Central Provident Fund (CPF) -- property prices and concerns about government accountability.
The growth outlook for Singapore's export-dependent economy is looking cloudy. The economy contracted a sharp 4.6 percent on-quarter in the second quarter and rose a feeble 1.7% from the year-earlier period.
"External headwinds have intensified amid the uncertainties in the global environment," DBS said in a note Wednesday, cutting its headline gross domestic product (GDP) forecast for the year to 1.8 percent, below the official forecast of 2.0-2.5 percent.
Calling Singapore's economy a "small boat in rough seas," it sees chances of a technical recession in the third quarter amid slowdowns in both the manufacturing and service sectors.
Anger over a surge in immigration, which pushed the island-nation's population up by over a million people since 2006 to more than 5.4 million last year, was partly to blame for the PAP's struggles at the polls in the last election. Publication in 2013 of a plan to increase the population to 6.9 million by 2030 was also unpopular.
The population increase spurred another issue that angered many Singaporeans: crowds on public transportation. That can also be a key opinion driver. After several disruptions of the subway system in July, satisfaction with the government fell around 4 percentage points to 76 percent from an April peak touched after Lee's death, according to a regular survey by Singapore-based Blackbox Research.
Since the 2011 election, the government has taken steps to address some of the concerns, tightening rules on hiring foreigners, including requirements that employers consider Singaporeans for some jobs before approving work passes.
But concerns over the number of foreigners in the country remain a talking point in this election. In its 2015 manifesto, the opposition Workers' Party cites a desire to maintain a "Singaporean core," particularly by focusing on increasing the country's birth rate, while holding the number of foreign workers steady.
Concerns over healthcare and retirement savings also dogged the PAP in the last election.
In an effort to address some of the healthcare concerns, the government will begin universal health insurance for Singaporeans and permanent residents in November. The program will charge higher premiums -- sometimes more than double the existing government-provided insurance program -- but will offer more coverage and subsidies for those with lower incomes.
But the government has resisted some opposition calls for universal healthcare.
"There is no way of giving something to everyone … without raising taxes on the middle-income group," Tharman Shanmugaratnam, the deputy prime minister, said in a recent speech which was posted on the Facebook page of Prime Minister Lee Hsien Loong, who is Lee Kuan Yew's son.
The country's mandatory retirement savings plan, the CPF, is also a continuing concern for some Singaporeans. The government's moves to increase the minimum age for collecting the funds, in line with life expectancy increases, and to increase the "minimum sum" which must be set aside as an annuity have proved unpopular. The interest rate paid on CPF savings -- which currently ranges from 2.5 percent to 4.0 percent -- is also a point of contention. That comes in above Singapore's consumer price inflation, which fell 0.4 percent on-year in July.
"Even if it was a 6 percent return, this is nothing to shout about," opposition party National Solidarity Party candidate and acting secretary-general Lim Tean, a legal consultant, said, according to the party's Facebook page. "If the government really cared for its people, it will be returning you better returns on the CPF."
He has called for a 15 percent return on CPF funds, according to a report by Today newspaper.
By comparison, Singapore's 10-year government bond is currently yielding around 2.8 percent. The return of the U.S. Social Security program -- which unlike the CPF's defined-contribution model is a defined-benefit plan -- was estimated at around a 6.5 percent at its best at the end of last year.
Runaway property prices have typically been a hot topic ahead of general elections. But this time around, housing prices are on the wane after around four years of cooling measures from the government and as expected supply completions begin outstripping demand. After years of price increases, however, voters still aren't pleased.
"Tighter mortgage lending standards and curbs on foreign purchases, along with slower immigration, have pushed down housing costs," Daniel Martin, an economist at Capital Economics, said in a note this week.
After so many years of one-party rule, many are concerned about government accountability and transparency -- especially as politicians' salaries remain among the highest globally, spurring accusations that they are out of touch with ordinary Singaporeans, particularly on income disparity.
The prime minister's annual salary is around 2.2 million Singapore dollars ($1.56 million) a year, making him the highest earning country leader globally, while members of parliament were paid around 192,000 Singapore dollars a year in 2012, according to media reports.
Singapore's median gross monthly income was around 3,770 Singapore dollars a month in 2014, according to government data.
"A diverse parliament is critical in assisting the executive to make sounder judgments about policy trade-offs," the opposition Workers' Party said in its manifesto. "A parliament monopolized by one party fails the test of rigorous debate and voting in forging sound policies."
Others are more blunt: "The PAP has an overwhelming majority in parliament. So do we need another person to vote yes to the PAP's policies," asked Jeannette Chong-Aruldoss, a candidate for the opposition Singapore People's Party, in a Sept. 6 speech posted on Facebook.
While the voting in Singapore is considered free and fair, the ruling party has in the past taken extraordinary steps to push voters away from choosing opposition candidates, including withholding funds for upgrading public housing projects in districts which don't vote for the PAP; around 80 percent of Singaporeans live in public housing projects.
--Nyshka Chandran contributed to this article
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1