No coalitions please, we're British

Seats are hard to come by at the House of Commons in Westminster. But the way to win one - the only way - is simplicity itself: you have to claim more votes than any other candidate in one of the UK's 650 electoral constituencies. If one party can win 326 of these mini-elections - and usually either the Conservatives or Labour can - then the keys to the kingdom are theirs. But finishing second in constituencies up and down the country is worthless, as the Liberal Democrats would gladly confirm.

"The electoral system in the UK is not proportional, and can indeed be wildly disproportional. You have a first-past-the-post system that's very unkind to smaller parties, and extremely unkind to parties with a large [geographical] spread in their votes," Alan Convery, lecturer in politics at the University of Edinburgh, notes.

The popular vote, that eternal barometer of democratic elections around the world, is ultimately meaningless in the UK. This is best displayed by a quick glance at the top three parties' performance in 2010:

The Conservative Party - 36.1 percent of popular vote, 306 seats.
The Labour Party - 29.0 percent of popular vote, 258 seats.
The Liberal Democrats - 23.0 percent of popular vote, 57 seats.

No higher learning certificate in mathematics should be required to spot the disparities here.

No majority on horizon

The traditional defense of this first-past-the-post system, Convery explains, was that the system did tend to deliver strong, majority governments. But in 2015, just as five years earlier, both Prime Minister David Cameron's Conservatives and Ed Miliband's Labour Party look set to fall as many as 50 seats shy of a majority.

"You could argue that this system was a stitch-up between the two main parties," Convery tells DW, "but if neither of them is going to get what they want out of it, then that might start to prompt them to think: 'Well, do the disadvantages of this system start to outweigh the advantages, if the holy grail of a majority government is no longer possible?"

In the event of a "hung parliament," where no single party has a majority of seats, several solutions are possible. These include a formal coalition - like the current uneasy union between the Conservatives and Liberal Democrats - or a minority government that seeks to legislate by securing opposition support on each vote.

Despite the UK's best efforts to encourage voters, effectively, towards a two-party system at general elections, people look set to give serious support to seven different parties on May 7. Whichever smaller parties can claim the most actual seats - not votes - could hold the balance of power in parliament.

Painting Westminster tartan

Remarkably, pollsters currently predict that the Scottish National Party (SNP) will become the third-largest power in the House of Commons after the Tories and Labour. Despite only competing in Scotland's 59 constituencies - less than 10 percent of the total - the SNP looks capable of winning anywhere between 30 and 55 of those seats.

This has prompted David Cameron to turn his attention north of the border as the election campaign begins, warning that Labour is planning an alliance with the SNP.

At the last pre-election Prime Minister's Questions - the weekly chance for the leader of the opposition and other MPs to quiz the PM in the House of Commons - Cameron referred to Miliband as "Salmond's poodle." He was talking about Alex Salmond, former leader of the SNP until Nicola Sturgeon took over following last year's independence referendum.

"They've opened the joint [bank] account - unlimited overdraft, obviously," Cameron, who is seeking to argue that the UK's economic recovery is only safe in Conservative hands, quipped.

Labour leader Miliband has ruled out a formal coalition with SNP, saying there would be "no SNP minister in any cabinet I lead," but Scottish lecturer Alan Convery believes that some kind of informal deal is at least possible.

Adding green, and purple, to political spectrum

For now, both Cameron and Miliband assert that they have not given up hope on securing a parliamentary majority - with neither leader keen to be drawn on the issue of future alliances. Both Labour and the Conservatives are polling at around 33 percent of the vote, projected to win in the region of 280 seats in parliament at this stage.

Next in line are the left-leaning Liberal Democrats, set to take a huge hit after their wildly unpopular alliance with the Conservatives from 2010. They're currently polling almost 10 percent down on their record haul from 2010.

The euroskeptic United Kingdom Independence Party, led by former Tory Nigel Farage, is next in line in terms of the popular vote. However, UKIP's estimated 10 percent national support could conceivably translate into just five or six parliamentary seats, or even fewer, according to current predictions. Despite the party's remarkable haul in European Parliament elections last year, Convery said this UKIP success was another quirk of the UK election system, where "protest votes" against the two main parties are usually lodged at minor elections.

"British voters seem to make a distinction between voting at different levels and in different elections with different issues at stake, and in addition to that, the first-past-the-post electoral system will constrain somewhat UKIP's advance," Convery said. "So, they're going to concentrate on the seats where they think they can win - the two seats they currently hold and then other seats where they think that the demographics and the political situation is favorable to them."

In his book "The Purple Revolution", serialized in a right-leaning newspaper in the run-up to the vote, Farage says he would step down as UKIP leader if he fails to win his constituency, South Thanet, in Kent in the southeast of England.

Similarly, the Greens - led by Australian Natalie Bennett - look set for their best-ever haul in terms of votes, and yet they might struggle simply to defend their single seat in Brighton in the south of England.

In Thursday's sole televised debate ahead of the May 7 ballot, the leaders of the Conservatives, Labour, the Liberal Democrats, UKIP, the Greens, the SNP and Welsh nationalist party Plaid Cymru will all lock horns.