Liberal MP Sarah Henderson is projected to retain the marginal seat of Corangamite in Victoria's south.

With more than 70 per cent of the vote counted, Ms Henderson was leading on first preferences, but has seen a 1.3 per cent swing against her to Labor.

The Country Fire Authority's (CFA) ongoing workplace dispute was predicted by some to have had an affect on voters in the seat.

The dispute over an enterprise bargaining agreement for career firefighters has created anger amongst the volunteers.

Volunteers unhappy with the State Labor Government's handling of the deal have campaigned outside polling stations.

The dispute has dragged on for months and led to the resignation of state cabinet minister Jane Garrett and the chief executive of the CFA, Lucinda Nolan.

Prime Minister Malcolm Turnbull also intervened, campaigning with Ms Henderson, and pledging to protect the role of the volunteers as one of the Government's first priorities if re-elected.

But Labor's Kim Carr said there had been swings to Labor in seats targeted over the issue.

Ms Henderson won the seat in 2013.