Dual by-elections in Victoria are too close to call but Werribee appears to be no longer a safe Labor seat and the Greens are trailing the Liberals in the Prahran electorate.
Political pundits will be scouring the results for clues about Labor's electoral fortunes at state and federal levels.
The two Victorian polls in Werribee in Melbourne's west and Prahran in the city's inner east marked the first time Premier Jacinta Allan and new Opposition Leader Brad Battin had been put to the test at the ballot box.
Labor traditionally holds Werribee but the party has slipped in the polls.
The resignation of former treasurer Tim Pallas triggered the by-election.
Early on Sunday morning, Liberal candidate Steve Murphy had 29.04 per cent of the primary vote with Labor's John Lister on 28.71 per cent.
Mr Murphy (49.45 per cent) was trailing Mr Lister (50.55) on a two-candidate-preferred basis.
The Liberals had hoped to secure an upset win there and also bag Prahran, a Greens stronghold up for grabs after MP Sam Hibbins quit in disgrace following revelations he had an affair with a staffer.
Early on Sunday morning, Liberal Rachel Westaway had 36.24 per cent of the primary vote with Greens candidate Angelica Di Camillo, an environmental engineer and climate strategist, on 36.18 per cent.
Former tribunal member Ms Westaway (51.6 per cent) was ahead of Ms Di Camillo (48.4 per cent) on a two-candidate-preferred basis.
Labor did not run a candidate in Prahran.
Cost-of-living emerged as the main concern for voters, along with housing attainability.
The Victorian Liberals also campaigned heavily on crime, with high-profile murders and knife attacks in Prahran and Werribee attracting attention in recent months.
Ms Allan touted her government's cost-of-living support measures as she backed Labor's Werribee candidate, local teacher and CFA volunteer John Lister, calling the opposition divided after a December leadership spill.
Mr Battin hit back, accusing the government of acting more like an opposition as he campaigned for his party's candidate, former policeman and army trooper Steve Murphy.
Some 104,000 people were enrolled in the two areas, with 28 per cent of Prahran voters and 29 per cent of those in Werribee casting ballots early or by post.
