The leader of election winners Move Forward was unopposed in the contest but struggled to muster the required support of more than half of 749-member the bicameral parliament, despite the backing of his eight-party alliance.

Another vote is expected to be held next week, which Pita can contest if nominated again.

The progressive Move Forward party and its alliance partner, Pheu Thai, thrashed conservative pro-military parties in the May 14 election, seen widely as a resounding rejection of nearly a decade of government led or backed by the royalist military.

Thursday’s vote was a critical test of Pita’s political clout and a gauge of the opposition to his party’s anti-establishment agenda, which includes removing the military from politics, curbing business monopolies and amending a law that prescribes long jail terms for insulting the monarchy.

His defeat was the latest blow in a torrid two days for the 42-year-old, U.S.-educated Pita, who saw two legal complaints against him gain momentum on the eve of the vote, including a recommendation to disqualify him, prompting hundreds of demonstrators to gather and warn of moves afoot to keep Move Forward from power.

Pita’s determination to pursue Move Forward’s agenda has put him at odds with a powerful nexus of conservatives and old-money families that have loomed large over Thai politics for decades, and had been expected to try to thwart him in parliament.

Despite winning the election on massive youth support and popularity in the capital Bangkok, Pita needed to win over some of the 249 members of the conservative-leaning upper house Senate, which was appointed by the military after a 2014 coup.

(Reporting by Panarat Thepgumpanat, Panu Wongcha-um, Orathai Sriring and Chayut Setboonsarng; Writing by Martin Petty; Editing by Lincoln Feast and Kanupriya Kapoor)