Final opinion polls pointed to 43-year-old Muscat's Labour Party (PL) retaining power with a reduced majority.
Final opinion polls pointed to 43-year-old Muscat's Labour Party (PL) retaining power with a reduced majority, four years after it swept into office on a redistributive, pro-business and socially liberal platform which has sustained Malta's recent economic success story.
But with 20 to 30 percent of the 341,856 registered voters still undecided in the final days of the campaign, analysts had not ruled out a surprise change of government as a result of the fallout from the so-called Panama Papers revelations.
Simon Busuttil, leader of the opposition Nationalist Party (PN), has framed the vote as a choice between change and allowing Malta's international reputation, and its prosperity, to be shredded by a series of scandals.
Muscat went to the polls a year early after his wife Michelle Muscat was accused of being the beneficial owner of a secret Panamanian shell company used to bank unexplained payments from Azerbaijan's ruling family.
The premier's chief of staff and a government minister have separately admitted having their own, previously undeclared Panama-registered companies, following revelations from last year's massive data leak from the Mossack Fonseca legal firm based in the Central American country.
Muscat came under fire for not firing the two men and the allegations against his inner circle have since broadened to include claims kickbacks were paid in relation to a controversial investment-based citizenship scheme and a gas supply deal with China, as well as bank licensing.
Shortly before calling the election, Muscat asked a magistrate to look into the allegations against his wife and vowed he would quit if he was shown to have an undeclared offshore account.
"It would have been the easiest thing in the world for me to weather the storm on the seat of power, while waiting for the magisterial inquiry to clear my name before calling an election," he said.
"However, in those few months the economy would have been damaged and jobs would have been lost," he said in defence of his decision to go to the polls.
Ballot stations close at 10pm (2000 GMT) and turnout in Malta is usually over 90 percent.
An antiquated manual vote-counting system, being used for the last time, means no reliable indicator of the result will be available before midday on Sunday.
Veterans of Malta's politics say most voters have life-long allegiances to one of the two main parties, which explains why Muscat appears to have been unscathed by the deluge of charges against people close to him.
"I have been Labour since I was born, and I will be Labour till I die," said Muscat supporter Frank Abela, who is about to retire after a career in the oil industry.
But he said Labour loyalists were not indifferent to the corruption claims.
"An allegation is one thing, an investigation is another thing and being found guilty or innocent is the final verdict. I'm 100 percent convinced he (Muscat) is clean. Regarding the other people, we will find out in due course."
John Zarb, a local butcher, echoed his faith. "Joseph knows he made sometimes mistakes and he is going to arrange everything after the election. Is he clean? Absolutely, yes!"
Pensioner Louis Attard and postgraduate student Marie Claire Finger struck different notes.
Attard said the foundations for Malta's economic success -- it is growing three times faster than the eurozone as a whole -- were laid before he took power.
"He is doing well with what he found. It's not on his merit," Attard said.
Finger said the premier should have sidelined any officials with the shadow of corruption hanging over them.
"Personally I think that it is embarrassing... to say I come from a country going through these things at the moment," she told AFP.
"I hope there will be a change."