CHARTS: How the latest opinion poll affects possible coalition scenarios

This year's general election is one of the most unusual in recent history.

Since the end of 2014, we've seen Prime Minister David Cameron's Conservatives close the gap to Labour, and both are now neck and neck at 33% each, according to Lord Ashcroft's final poll from the day before the election.

Below, we have created a terrifically useful chart that visualises the possible coalition scenarios after the vote - as none of the parties are likely to be able to form a government on their own.

UKIP is still holding up at around 11% of the national vote.

The Green surge seems to have levelled off at 6%.

The Lib Dems appear stuck at 10%.

Here is the full Ashcroft analysis:

And the Scottish National Party looks set to all but wipe Labour out in Scotland by taking as many as 50 seats north of the border.

Since 1979, only three election campaigns (1992, 1997, and 2005) saw less movement in the polls than we've seen over the past year.

In terms of seat projections, this means that neither of the UK's two biggest parties look set to secure anything close to an outright majority of 323 seats (discounting Sinn Féin MPs who don't take their seats in parliament).

So we're now almost certain to get a coalition government (Election Forecast UK puts the probability of a hung parliaments at 97%).

But who looks more likely to form it? Here are some possible scenarios.

The chart below shows the projected number of seats for various coalition possibilities versus the magic 323 needed to form a stable government. As you can see, only one (a Labour/Liberal Democrat/SNP deal) looks like it would comfortably cross that line:

Here's what that looks like when you break it down by party (we've changed the scale of chart so that the make-up of the coalitions are easier to see). Either Labour or the Conservatives would comfortably remain the largest party in any government, but both will need to get through some difficult negotiations if Ed Miliband or Cameron is to get into Downing Street at the first attempt:

Two things to note from this chart. Neither Labour nor the Conservatives look very likely to be able to form a stable government with the Liberal Democrats alone. That is significant, because it means that at least one of the UK's smaller parties is likely to hold the balance of power for the first time since the 1970s where SNP votes helped to bring down James Callaghan's Labour government.

The second thing worth pointing out is that the Conservatives are now overwhelming favourites to secure the largest number of seats. This could be very important since last week Lib Dem leader Nick Clegg told the BBC that he would give the party with the largest number of seats the first chance to form a government.

He said: "In a democracy, the party with the greatest mandate from the British people - even though they haven't got a majority - seems to me, to us, to be the party that has the right to try to assemble a government first. They may not succeed, but they should surely be given a chance to succeed."

If Cameron can persuade the Democratic Unionists to join him, he could come within 10 seats of security a stable government by renewing his partnership with the Lib Dems (if current polling proves a good guide to the result). But at this stage it's getting harder and harder to see where those extra 10 seats are going to come from.

If he fails, it now looks hard to imagine Labour being able to do any better without entering into talks with both the Lib Dems and the SNP - something that Clegg has ruled out for his party. That, then, leaves the prospect of a second election on the table.