Malaysians voted on Sunday with one of the world's longest-serving governments seeking to stave off a first-ever defeat against an upstart opposition that pledges sweeping reform.
Lines of up to one kilometre (0.6 miles) long were reported as voting got under way at more than 8,000 polling sites nationwide in an apparent heavy turnout, which analysts have said may boost the opposition.
But voters took to the Internet in droves to accuse Prime Minister Najib Razak's government of trying to steal the election, as indelible ink that he touted as a guarantee against voter fraud was found to easily wash off.
Until Sunday, the supremacy of the ruling bloc dominated by the United Malays National Organisation (UMNO), and now led by Najib, has been unthreatened since independence in 1957.
But the diverse Pakatan Rakyat (People's Pact) opposition alliance captained by charismatic former UMNO star Anwar Ibrahim stunned the country with historic gains in 2008 polls and Sunday's vote has been keenly awaited ever since.
"There is clearly, undeniably, a major groundswell and a major shift among the population across ethnic lines," Anwar, 65, said after he cast his ballot in a polling centre in his constituency in the northern state of Penang.
"Insyallah (God willing), we will win."
The ruling coalition is widely given the edge but Anwar has been feted by crowds in the tens of thousands on the stump, and recent opinion polls have suggested a razor-thin margin.
Pakatan has gained traction with pledges to end ruling-party corruption and authoritarianism, and to reform controversial affirmative-action policies for majority Malays that Anwar says merely prop up a corrupt Malay elite.
His back to the wall, Najib has offered limited political reforms but a largely stay-the-course vision for the Muslim-majority nation while touting solid economic growth.
Polls close at 5:00 pm (0900 GMT) with first results expected within hours.
The opposition has raised the spectre of a disputed result by accusing Najib's coalition, known as the Barisan Nasional (National Front), of numerous poll violations.
Among them, Anwar says tens of thousands of "dubious" and possibly foreign voters were flown to key constituencies to sway results. The government has said the flights were part of a voter-turnout drive but has provided no details.
Najib tweeted Sunday that no foreigners were drafted in.
"We are committed to a fair election," he said.
But voters angrily complained about the ink, introduced for the first time and touted by Najib and the Election Commission -- widely viewed as Barisan-controlled -- as proving their commitment to fair polls.
After voting at Anwar's polling centre, Halim Mohamad, 77, said the ink, applied to a voter's finger and supposed to last several days, washed right off.
"This is cheating. I was shocked when it came off," he told AFP, showing his cleaned index finger.
"I complained to an Election Commission official and he just laughed."
Anwar was a former deputy premier until his ouster in a 1998 power struggle and six-year jailing on sex charges widely viewed as trumped up.
He later brought his pan-racial appeal to the once-divided opposition, dramatically changing its fortunes.
Najib has warned of chaos and racial strife under the occasionally fractious Pakatan, which includes Anwar's multi-racial party, one led by ethnic Chinese, and another representing conservative Muslim Malays.
Najib's ethnic Malay-dominated regime retains powerful advantages, including control of traditional media, key institutions and an electoral landscape critics say is biased.
Campaigning has been marred by hundreds of reports of violence, including two small explosions, but no deaths.
"It's a tight run. But I'm not scared, I'm excited," retiree H.Y. Ong said of the race before voting in the capital Kuala Lumpur.
"The times have changed, they (the government) need to change. Money politics should be controlled," he added, while not divulging his voting preference.