Parliamentary elections that sparked riots last month left the Communists one vote short of the 61 required to elect a replacement for their veteran communist leader Vladimir Voronin, who is unable to stand for a third term.
Voronin, who says he hopes to keep a decision-making role, has since been elected speaker of parliament in Europe's poorest country.
Parliament opened its session in a large meeting hall with the Communists proposing Prime Minister Zinaida Greceanii as a presidential candidate. She is seen as a loyalist who is easily controlled by Voronin.
If Greceanii fails to secure the necessary votes, parliament must hold a second ballot. If the second ballot fails, the chamber must be dissolved and a new parliamentary election held.
"The chances of a president being elected in the first round are just about zero," said Igor Botan, head of the Adept think-tank in Moldovan capital Chisinau.
He said the Communists stood a better chance of securing victory for their candidate in a second vote, because "the stakes are now higher" with the threat of a new parliamentary election.
In her address to MPs, Greceanii vowed to uphold the sovereignty and neutral status of the former Soviet republic. She also pledged to promote Moldova's integration with Europe and intensify efforts to solve an 18-year old "frozen conflict" with separatists in the Russian-speaking Transdniestria region.
"I will direct all my strength to enhancing Moldova's statehood," she told the session.
"A solution to Transdniestria is absolutely necessary for the existence of our state. We need to resume negotiations on Transdniestria in an internationally-recognised format."
New turmoil possible
Plunging Moldova into a new parliamentary election could produce new turmoil in the country wedged between Ukraine and EU member Romania, with which is shares historical and linguistic ties.
After the April elections, students disheartened by an economic crisis and the prospect of further communist rule ransacked the presidential and parliamentary buildings. The opposition said the election was rigged and accused the police of brutality against protestors.
Serafim Urechean, head of the opposition 'Our Moldova' party, said all three opposition groups, with 41 seats in parliament, would remain united to defeat Wednesday's vote.
"We will stand by our position until the very end," he said. "We want an early election and we will get one."
Voronin said the violent protests in April amounted to an attempted coup fuelled by Romanian support.
In power since 2001, he has overseen stability and economic growth in the country.
But he has been unable to solve the rebellion in Transdniestria, a sliver of land populated by Russian speakers that broke away in 1990 because of fears Moldova might one day unite with Romania.
Voronin was at first close to Russia, then fell out with Moscow over its peacekeeping troops based in Transdniestria, which he said blocked any resolution to the conflict. He has in the past year restored closer ties with Russia.
The three opposition parties - Liberal Democrats, the Liberal Party and Our Moldova - are all broadly more pro-Romania and stand for closer links to the EU.
(EurActiv with Reuters.)
