For the first time since its majority victory in 2013, Stephen McNeil's Liberal government will be put to the test on Tuesday as voters in three electoral districts cast ballots to choose new provincial representatives.

The byelections in Cape Breton Centre, Sydney-Whitney Pier and Dartmouth South are the result of two retirements and the death of one MLA.

New Democrats Gordie Gosse and one-time deputy premier Frank Corbett both retired in April, while Liberal backbencher Allan Rowe died in March from a brain aneurysm.

The polls close at 8 p.m.

The three parties in the legislature are all fielding candidates.

Edna Lee, the Progressive Conservative candidate in Cape Breton Centre, and Gordon Gamble, who represents the party in Dartmouth South, are both trying a second time to win races they lost in 2013.

In Dartmouth South, there's also an independent candidate.

Eligible voters in the three ridings:

Dartmouth South: 16,940

Cape Breton Centre: 13,302

Sydney-Whitney Pier: 18,238

Charlene Gagnon was almost forced to withdraw from the race because of an Elections Act provision that suggested salaries had to be counted as election spending.

The legislature had passed an amendment in April that exempted salaries from the rules, but it hadn't come into force until Nova Scotia Premier Stephen McNeil ordered it proclaimed in June.

That decision allowed Gagnon to continue campaigning.

In the last election, the New Democrats managed to hold the two Cape Breton seats but by much smaller margins than in previous campaigns.

In fact, in 2009, Frank Corbett took 80 per cent of the vote in Cape Breton Centre. Gordie Gosse took 71 per cent of the vote that year. The former House Speaker represented Sydney-Whitney Pier for 12 years. Corbett held his seat 17 years.

Charlene Gagnon was almost forced to withdraw from the race. (CBC)

Dartmouth South has a more checkered political past.

Allan Rowe won it from the New Democrats in 2013 by more than 1,000 votes, but the riding has been represented by all three main parties since 1999.

Both opposition parties claim Tuesday's vote is a chance for voters who are unhappy with the Liberals to send the premier a message.

McNeil doesn't see it that way — in fact, even if his party lost all three races, it wouldn't change much in the House.

The Liberals currently hold a comfortable majority in the Nova Scotia legislature with 32 Liberals, 10 Progressive Conservatives, five New Democrats and an independent.

Voter turnout is expected to be about the same as during general elections.

In 2013, roughly 59 per cent of eligible voters cast ballots. During four byelections held between 2009 and 2011, between 51 per cent and 59 per cent of voters cast votes.