Government general-secretary Victor Ponta, a former premier, told The Associated Press in an interview that Prime Minister Sorin Grindeanu is a guarantor of stability and predictability in the East European country.
Grindeanu is "the good option, the positive option, the option for the future," Ponta said.
The ruling Social Democratic Party withdrew political support for Grindeanu last week, saying he hadn't implemented the party agenda.
Grindeanu, in office since January, denies he's underperformed and says party chairman Liviu Dragnea is seeking greater control over the party. Dragnea is barred from being premier himself because of a 2016 vote-rigging conviction.
Parliament will hold the no-confidence vote Wednesday. If it fails, Grindeanu remains prime minister. If it passes, the ruling coalition will propose a new candidate for premier who is then nominated by President Klaus Iohannis.
The move to oust Grindeanu gained momentum Monday after the chairman of the ethnic Hungarian party, Hunor Kelemen, said the Social Democrats should be allowed to "change ministers and governments" if they wished. He spoke after the Social Democrats approved a proposal to make March 15 - a day when Hungarians celebrate the 1848 Hungarian revolution - a national holiday for ethnic Hungarians.
Grindeanu believes that if he's ousted a loyalist to Dragnea will be appointed.
Ponta said the conflict has provoked "total astonishment" among Western allies and that it began after the Constitutional Court in May upheld a ruling that no one with a conviction can serve as a minister.
"From this moment... the conflict started, the (party) leader irrevocably can't be prime minister and the prime minister ...then said we have a long-term government that is stable," he said.
Ponta said Dragnea's style of leading the party, which voted unanimously to withdraw support and expel Grindeanu, was reminiscent of communist-era politics: "Only then was there unanimity, the leader decided absolutely everything," he said, predicting that the crisis could split the party, the biggest in Romania.
The ruling coalition needs 233 votes to oust the government in the 465-seat legislature. It has 247 seats.
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