Sixteen years of Labor government in New South Wales is set to end today, with analysts predicting a defeat of historic proportions.

Voters are heading to the ballot boxes this morning, with predictions of a landslide victory for the coalition.

But despite this fundamental shift in state politics, the campaign has been overshadowed by a string of national disasters and crises at home and overseas.

The result has long seemed a foregone conclusion, with the latest polls suggesting Labor will struggle to win even a quarter of the seats in the Lower House.

Aside from the Coalition, Labor is facing the added threat of the Greens snatching up two of its once-safe inner city seats.

ABC election analyst Antony Green believes Labor will lose some seats it has held for 100 years.

Based on Friday morning's two opinion polls, Green's election calculator suggests that Labor's share could be as few as 13 seats in the 93-seat Lower House.

That is against a likely Coalition haul of up to 75.

"This election is going to see the biggest turnover of MPs in New South Wales history," Green told AM.

"This is bigger than the turnover that came with Federation. After this election over half of the MPs in the Lower House may be new Members of Parliament."

Even with predictions like that, Premier Kristina Keneally is still saying her opponent Barry O'Farrell will not have a mandate on Monday.

"If the polls today are correct and Mr O'Farrell is slated for victory, it'll be a victory without a mandate, because he's not telling people what it is he will do," she said.

Ms Keneally voted in her electorate of Heffron at Rosebery this morning, while Mr O'Farrell will cast his vote in Linfield in his northern electorate of Ku-ring-gai.

Tactics backfire

A lot of observers have judged Ms Keneally the winner in head-to-head debates with Mr O'Farrell, but that does not seem to have mattered.

Nor has the party's election advertising or its intensive campaigning.

In fact, in some electorates Labor's tough tactics may have backfired.

In Kogarah in Sydney's south, Labor funded a direct mailout to voters.

The writer, Joanne Goudie, describes herself as a Hurstville conveyancer and mother of two.

In the letter, she says she has always been a Liberal supporter but because of the record of Liberal candidate Miray Hindi, she is urging voters to keep Labor's Cherie Burton as the elected member.

The move angered Ms Hindi who accused Labor of dirty tricks.

"That letter shows how desperate Cherie is. After her own dishonesty has been exposed in the last few days, she ran out of options," she said.

"She used someone who doesn't even live in the electorate of Kogarah, someone who doesn't even live in the area, trying to tell people not to vote for me.

"That is disgusting. This is Labor Party dirty tricks."

Green threat

Labor also has a fight on two fronts: on the right from the Coalition, and on the left from the Greens.

Polling suggests that for the first time there could be two Greens MPs in the New South Wales Lower House and if so, they will not just be knocking off disposable backbenchers.

The Greens' Leichhardt Mayor Jamie Parker could take the seat of Balmain from the high-profile Education Minister Verity Firth

Mr Parker is upbeat about what a win in the seat would mean for the party.

"It would be a breakthrough in terms of people's understanding of the Greens' influence and involvement in politics here in New South Wales. It would demonstrate to people that we reflect their values and priorities," he said.

In the neighbouring seat of Marrickville, Deputy Premier Carmel Tebbutt is under threat from the Greens' Fiona Byrne.

"It's going to be a tough election in Marrickville. I've always understood that. I'm in the fight of my life," Ms Tebbutt said.

Labor has sought to brand the Greens candidate as an extremist, bent on taking an anti-Israel boycott she implemented as Mayor of Marrickville to state parliament.

But Ms Byrne says she will not take up the issue as a state MP.

"I think Labor are pushing these issues out of desperation," she said.

"If Labor had expended the same amount of energy actually delivering for New South Wales, then state Labor may not actually be in the position they're currently in."

Labor's situation is so dire that its real fight is to pull back enough seats to field a credible shadow cabinet.

And if there is electoral carnage tonight, the federal party and the Federal Government will be having to ask itself some very hard questions about how to win seats in the crucial state of New South Wales at the next federal election.

Polling booths close at 6:00pm AEDT.