But their majority saw a sharp drop, leading some to wonder whether the appeal may be fading along with memories of the country'sviolent history, and amid rising concerns of corruption.
The main opposition Cambodia National Rescue Party (CNRP) gained significant ground, despite a government-controlled media, and allegations of intimidation and deletion of eligible voters from the register.
The CNRP "hammered away at hot button issues such as loss of land, environmental impact of development, and corruption," said Carlyle Thayer, a South-East Asia expert at the Australian Defence Force Academy in Canberra.
The ruling party also "lost traction" by fielding long-serving officials ahead of younger candidates, he said. "This suggests the CPP was complacent."
The CNRP won 55 parliamentary seats to the CPP's 68, up from 24 seats to 73 in 2003 and 26 against 90 in 2008. In both those earlier elections the party ran as the Sam Rainsy Party, named after the former exile and current leader of the party.
Hun Sen has historically relied on the gratitude of the mostly poor, rural voters for improvements in infrastructure and security,after the devastating conflicts of the late 20th century.
But younger voters never lived through the Khmer Rouge regime that saw 1.7 million Cambodians perish during 1975-79, Rainsy said.
"Thirty years ago this may have been relevant, 20 years ago still relevant, but now not relevant," he said. "Seventy per cent of the population were born after the Khmer Rouge." And the younger generation, more connected to electronic and social media, look enviously to the relative wealth of neighbouring countries like Thailand, he said.
"They watch foreign films, they use Facebook, they see: 'oh,Cambodia is relatively backward, Cambodia is corrupt'," he said.
But with one-third of the population earning less than a dollar a day, the social media is probably reaching only the small middleclass that grew out of the economic growth of Hun Sen's 28-year rule,and the well-connected officials and their families who amassed moreconsiderable fortunes.
"The young who take part in (opposition) parades, many of them arefrom well-off families, sons of apparatchiks," Rainsy boasted.
"But"there are also poor people and the unemployed." The ruling party may also have lost some support due to its granting of land concessions to private firms and the subsequent evictions, said Moeun Tola, programme chief of the Community LegalEducation Center.
"I think those who were affected by land-grabbing vote for theopposition," even though many evictees who protested had found theirnames wiped from the voter list, he said.
The CNRP pledged to support land rights, he said.
But Cabinet spokesman Phay Siphan rejected the need to do anysoul-searching, saying Sunday's ballot simply proved Cambodia was a truly democratic country.
"I don't think people reject CPP policy," he said.
Rather, he attributed the opposition's gains to racist rhetoric intheir campaign.
The CNRP has always labelled the Hun Sen government "Vietnamese puppets," because they were the first Vietnamese-backed governmentafter the Khmer Rouge, with Hanoi's troops stationed in Cambodia well into the 1980s.
Many Cambodians still distrust today's Vietnamese migrants, who they say enter the country illegally and take Cambodian jobs. Theopposition has capitalized on that dislike, regularly referring to ethnic Vietnamese people by the derogatory term "Yuon." The CNRP claims it would have won if the election had been fair,and on Monday rejected the results of the National Election Commission, calling for an investigation with the participation ofdomestic and international monitors.
The CNRP said one audit of the electoral roll earlier this year by the Washington-based National Democratic Institute that found 1 in 10 registered voters did not appear to exist.
The party also cited a finding by local election monitor the Committee for Free and Fair Elections that 1.25 million voters could be disenfranchised due to problems with the list.
About 9.6 million of Cambodia's 15 million people were registeredto vote.