The B.C. Poll Tracker has been updated with the latest polling data published Monday evening. Check here for the latest numbers.

Tuesday's provincial election in British Columbia is setting up to be the most uncertain and closest vote in over 20 years, as polls show the B.C. Liberals and B.C. New Democrats nearly tied in public support — a split that could give the edge to the Liberals' Christy Clark over John Horgan and the NDP.

According to the CBC's B.C. Poll Tracker, an aggregation of all public polls that will be updated throughout the day as the final polls of the campaign are published, the Liberals and NDP are tied at 39 per cent apiece.

That's a significant reversal of fortunes from a little over two weeks ago, when the gap between the two parties stood at seven points in the polls to the NDP's benefit.

The Greens follow in third at 19 per cent support, while about three per cent of British Columbians are expected to vote for other parties and independent candidates.

With these levels of support, the Liberals are narrowly favoured in the seat projection, with 44 seats to 41 for the NDP and two for the Greens.

While that points to the narrowest of majority governments, the B.C. Liberals have a higher seat ceiling and thus a better chance of winning than the NDP — running 10,000 simulations with these seat ranges gives victory to the Liberals 72 per cent of the time, with the NDP winning the most seats 28 per cent of the time.

The odds of a minority government stand at about one-in-five — significant for a province that hasn't had a minority government since the 1950s.

Polls hint at Liberal advantage

The seat projection model favours the Liberals in a close race largely because the party's regional support is more efficient than the NDP's. But while the race is otherwise a toss-up — two polls published Monday morning by Mainstreet/Postmedia and Ipsos/Global News give the NDP a statistically insignificant one-point lead over the Liberals — there are reasons to believe the Liberals could have the edge.

In the polls conducted partially or entirely in May, three have given the NDP the lead by a single point while two have given the Liberals a lead of two to four points. That suggests that the Liberals have the higher upside than the NDP. The Liberals have also been trending upwards at the tail-end of the campaign, while the NDP has stagnated or dropped.

The Liberals also potentially have a turnout advantage. Mainstreet finds that the Liberals have stronger supporters and give the party a three-point lead among those voters who are most likely to vote and least likely to change their minds.

Both Mainstreet and Ipsos give the Liberals a significant lead among older British Columbians, who also vote in larger numbers.

On leadership, in six polls conducted during the campaign that have asked who voters think would be the best premier, Clark has placed ahead of Horgan in five of them.

Metro Vancouver, Interior to decide result

Nevertheless, the margin is close enough in the polls that the popular vote could go in the NDP's favour. Which party will win the most seats, however, will depend on how those votes break down regionally.

In 2013, the B.C. Liberals won both the regions of Metro Vancouver and the Interior/North — the former by about five points and the latter by about 13.

The Liberals still look set to win the Interior/North again, leading with 48 per cent to 33 per cent for the NDP. The Liberals will thus be looking to hold onto the seats they have in the Interior and potentially pick up a few at the expense of the NDP. The trend line has been heading in the Liberals' direction in the region.

NDP Leader John Horgan gestures to indicate two days until election day while addressing supporters during a campaign stop in Vancouver on Sunday. (Darryl Dyck/Canadian Press)

Metro Vancouver, however, is trending against the Liberals. The polls now give the NDP about 42 per cent to 38 per cent for the Liberals, a swing of some nine points from 2013. That has the potential to move a number of seats from the Liberals over to the NDP.

But can the New Democrats win enough new seats in Metro Vancouver to make up for a lack of gains — or losses — in the Interior? Horgan's election hopes lie in a strong showing in and around Vancouver.

Breakthrough or bust for the Greens?

Additionally, the New Democrats will need to minimize their losses on Vancouver Island.

After flirting with the lead earlier in the campaign, Andrew Weaver's Greens have since fallen back, dropping to about 28 per cent and into a tie with the Liberals. The NDP still leads on the island with 40 per cent. But both the Liberals and NDP are trending below their 2013 levels of support on Vancouver Island, opening up some opportunities for the Greens.

Support for the Green Party, whose leader Andrew Weaver is seen above in Nanaimo, B.C., stands at 19 per cent a day before the vote. (Darryl Dyck/Canadian Press)

Attaining four seats and official party status in the B.C. legislature is within reach of the Greens, but it is looking like a bigger challenge than it was earlier in the campaign.

How the Greens do is perhaps the biggest unknown going into tomorrow's vote. Polls put the party at between 15 and 23 per cent support provincewide and between 20 and 35 per cent support on Vancouver Island. Within those bands of support lie everything from a breakthrough to a disappointment for Weaver and the Greens, with significant implications on the performance of the other parties.

Multiple outcomes possible

This all leaves the outcome of the B.C. election uncertain. The Liberals have a regional and turnout advantage that should give them the edge in a close race. They could also benefit from incumbency and so out-perform their polls, as has often been the case in other jurisdictions. That would turn a slim majority into a wider one.

The New Democrats could benefit from a breakthrough in Metro Vancouver or a decrease in Green support that, polls suggest, would boost the NDP more than the Liberals. But they could also under-perform their polls as they did in 2013.

And the Greens could prove to be efficient in getting their supporters out exactly where the party has a shot at winning seats — giving them official party status and potentially the balance of power in a minority government. Or the Greens could under-shoot their polling average, as the party has often done elsewhere in Canada.

Considering the margins of error in polls and the regional dynamics at play, such a narrow gap between the New Democrats and the Liberals could result in any of the above outcomes without the polls seriously missing the mark.

So surprises could be in store. All will be revealed after voting closes at 8 p.m. on Tuesday night.