Cambodian Prime Minister Hun Sen was among the early voters on Sunday, casting his ballot shortly after the polls opened in a national election his party is expected to easily dominate.

The veteran Cambodian leader was all smiles as he walked from his car to the polling station near his home in Takmau in Kandal province, south of the capital Phnom Penh. After casting his ballot, he declined to speak to reporters, presumably to conform to rules barring any sort of campaigning during the voting period.

Opposition leader Sam Rainsy visited a polling station near his party’s office in Phnom Penh, where hundreds of voters, particularly younger ones, greeted him enthusiastically, taking photos and a few bolder ones even hugging him.

“I am happy to see people flocking to vote,” Mr. Rainsy told reporters, though he himself cannot vote and is not on the ballot because he failed to register in time, being in self-imposed exile until earlier this month.

The exile was to avoid a jail term for convictions he said were politically motivated. He returned on July 19, only after receiving a royal pardon at the behest of Hun Sen, his longtime and bitter rival.

Mr. Rainsy, leader of Cambodia National Rescue Party (CNRP), said on Saturday that any gains his party makes against Mr. Hun Sen’s Cambodian People’s Party (CPP) would be significant, and would set the stage for a long fight for fair elections.

Mr. Rainsy’s party and nonpartisan groups charge that the ruling party uses the machinery of government and security forces in an unfair manner to reward or pressure voters. They also say that voter registration procedures were badly flawed, possibly leaving more than 1 million people disenfranchised.

The CPP and the government-appointed National Election Committee say the election process is fair.

“We are going backward in term of election fairness,” Mr. Rainsy told election observers.

Opposition parties had held 29 seats in the Assembly, but were kicked out of the body shortly before election campaigning began on the technical grounds that they had registered to run in the name of the new CNRP, formed by a merger of the two existing opposition parties under whose banners they had won their seats.

Despite the poor prospects for change, the campaign has generated great excitement, especially among young people in Phnom Penh, the capital. Large crowds of supporters of the two main parties staged spirited rallies that ended on Friday, with Saturday being an officially decreed “quiet” day with no campaigning allowed.

Mr. Rainsy told reporters that he knew the election was unfair, but that his party was taking part “to show the Cambodian people that we are with them.”

In a last-minute hitch, the independent Committee for Free and Fair Elections said on Saturday that the ink voters were supposed to stain their fingers to prevent them from voting twice was not indelible as claimed.

There are 9.7 million registered voters in a population of almost 15 million. Just over half the electorate is under 30-years-old.

The election campaign has not been marked by the kind of violence, including killings, which plagued past polls.

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