CHISINAU - Moldovans cast their ballots on Sunday in a presidential election and EU referendum at a pivotal moment that could bolster the small agricultural economy's drive to join the European Union.

Polls show incumbent Maia Sandu has a comfortable lead over her 10 rivals on the ballot, though the race will go to a Nov 3 run-off if she fails to reach the 50 percent threshold to win outright.

Polls show she is likely to face Alexandr Stoianoglo, a former prosecutor-general backed by the Party of Socialists, if the vote goes to a second round.

Sandu hopes to see a resounding "yes" at the referendum, which will decide whether to insert a clause into the constitution defining EU accession as a goal.

ALSO READ: EU agrees to open accession talks with Ukraine, Moldova

"Our fate is decided on Sunday. Everyone's vote matters, no matter where we are," she wrote on Facebook on Friday.

Polling stations, which opened at 7 am (0500 GMT), close at 9 pm (1800 GMT). The Central Election Commission is expected to issue early, preliminary results at a first news conference at 10 pm (1900 GMT).

Polls show a majority support joining the 27-nation bloc, though five of the candidates have told their supporters to vote "No" or boycott, saying the timing of the referendum is a ruse to boost Sandu's haul at the election.

READ MORE: New Moldovan government wins backing of Parliament

The referendum needs a turnout of at least a third of the people listed on electoral rolls for it to be deemed valid, even though the lists have not been updated in years despite many people emigrating.

A weak outcome for Sandu would set the tone for next summer's parliamentary elections, where political analysts say her PAS party will face a challenge to retain its majority.