Thai lawmakers are gathering Thursday to select a new prime minister, a process whose outcome is far from certain even though the country's most progressive party won both the popular vote and the most seats in the House of Representatives in the most recent election.

Thailand's May 14 election was regarded as a major political turning point. The reformist Move Forward Party's victory appeared to spell an end to nine years of unpopular army-supported rule. Two months later, it is unclear if that mandate for change will be honored.

Parliament is due to vote on whether to make Move Forward's leader, 42-year-old businessman Pita Limjaroenrat, the country's prime minister. His party captured 151 of the 500 House seats but has assembled a coalition government-in-waiting. The eight parties in the coalition won 312 seats combined, a healthy majority.

“This is a party leading a coalition, and they’ve won the election,” Thitinan Pongsudhirak, a political scientist at Bangkok’s Chulalongkorn University, said. “In most other countries, they would be in office by now.”

One of several potential roadblocks to Pita taking power is that the prime minister is elected through a joint vote of the House and the 250-seat Senate, whose members owe their positions to the military-backed regime established by a 2014 coup. Pita, or any other candidate, therefore needs a minimum of 376 votes to become head of government.

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The biggest bone of contention between the liberals backing Move Forward and the deeply conservative Senate is the campaign pledge of Pita’s party to amend a law that makes defaming the royal family punishable by three to 15 years in prison.

The monarchy is sacrosanct to members of Thailand’s royalist establishment, and even minor reforms that might improve and modernize the monarchy’s image are anathema to them. Move Forward’s coalition partners also have not endorsed the proposed legal change, and other parties ruled out joining the coalition because of the idea.

Thitinan thinks that given the massive voter support for Move Forward and the Pheu Thai Party, its top partner and political ally, Pita stands a good chance “because of mounting public pressure on the senators. It will depend on the will, the resilience and the intransigence of the royalist conservative establishment.”

But if Pita cannot win over enough senators, his options appear nil. The options for the eight-party coalition as a whole appear more viable.

One is for the Pheu Thai Party to put forward one of its members as a candidate for prime minister, a possibility that once would have been unthinkable.

Pheu Thai used to be the royalist establishment’s public enemy No. 1. The party is closely affiliated with former Prime Minister Thaksin Shinawatra, a billionaire populist who was ousted in a 2006 military coup, in part because his popularity rubbed royalists the wrong way.

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Thaksin-backed parties finished first in every election from 2001 until this past May but were blocked or forced from power each time. The 2014 coup, for example, seized power from a government that Thaksin’s sister, Yingluck Shinawatra, had formed.

Pheu Thai enrolled three of its members as potential prime minister candidates this year, including Thaksin’s daughter. Paetongtarn Shinawatra. It is a measure of the shift in political winds that Pheu Thai is now regarded as a party that royalists can deal with, compared with Move Forward, which they dismiss as radical.

Paetongtarn’s colleague, real estate developer Srettha Thavisin, is considered more likely to have his name put forward if Pita isn't election, at least partly as reassurance to the business community. But the possibility that any proposed coalition including Move Forward won’t be approved complicates the numbers game.

The departure of Move Forward would probably require Pheu Thai to enlist allies from among military-friendly parties, which it vowed, with hedging, not to do. In the long run, seeking such an alliance could erode Pheu Thai's credibility with supporters who stuck by the party and boost support for Move Forward while it's in opposition.

Another cost could involve ceding the prime minister’s seat to a newly enlisted coalition partner, the key one being the Bhumjaithai Party, which polled third in the May election and secured 71 House seats. The party's leader, Anutin Charnvirakul, was health minister in the outgoing government and has made no secret of his political ambitions.

If Pita and Move Forward somehow prevail -- and it could take several votes over a period of weeks -- their political survival still would sit on a knife’s edge.

There have been fears that Thailand’s conservative ruling establishment would use what its political opponents consider to be dirty tricks to cling to power. For a decade and a half, it has repeatedly utilized the courts and supposedly independent state agencies to issue questionable rulings to cripple or sink political opponents.

On Wednesday, the Election Commission said it concluded there was evidence that Pita had violated election law, and referred his case to the Constitutional Court for a ruling. If the court accepts the case and finds him guilty, he could lose his House seat, get kicked out of politics and face a prison sentence.

The alleged violation involves undeclared ownership of media company shares, which are banned for Thai lawmakers. Political scientist Thitinan describes the charge and other legal complaints against Pita as “bogus” and something many people, especially voters who backed him, would be unwilling to tolerate.

“It all depends on how far the royalist conservative establishment wants to go after Pita and prevent a democratic outcome,” he said.

Depending how they are resolved, the efforts to block Pita and Move Forward could prove dangerous and cause Thailand unnecessary pain, said Michael Montesano, a Thai studies expert who is an associate senior fellow at Singapore’s ISEAS–Yusof Ishak Institute.

“At the end of the day, the political system and those who would dominate need to move into closer correspondence with the realities of Thai society and with the aspirations of its younger, well educated members,” Montesano said. “The biggest question is whether this transition will be painful and even violent, or whether it will be constructive and thus serve the country’s future prospects."