For the third time in two years battle-weary Brits must trudge back to the polls.

In April, when Prime Minister Theresa May shocked the nation by calling an election, the result looked like a foregone conclusion.

The Conservative leader was miles ahead in the polls, well-liked – if not loved – by voters, and she had a monopoly on the election’s defining issue, Brexit.

Yet things quickly unravelled. While polls still point to a Conservative victory on June 8 (UK time), the outcome looks far less assured than it did a month ago.

Even allowing the polls – so wrong on Brexit, Trump and the last UK election – are not the trusted barometers they once were, the campaign’s final week promises to be a humdinger for those who relish political drama.

Here’s an armchair pundit’s guide to the main contenders:

Theresa May, Conservative

Before June 2016, Theresa May spent six successful years as home secretary, in charge of immigration and national security. She developed a reputation as a solid and efficient senior minister.

Theresa May has opted for tightly controlled election events. Photo: EPA

Following the shock victory for the Leave camp in the EU referendum, Ms May emerged as the clear choice to replace David Cameron. She was seen as a stable, moderate leader who could unite the party.

Once a “Remainer”, as PM Ms May has enthusiastically banged the drum for “a hard Brexit”  – including full withdrawal from the single market. And the Conservatives have maintained a consistent lead over Labour.

The Tories sought to frame the election as a presidential-style contest between the “strong and stable” Ms May and the “radical” and “pacifist” Mr Corbyn. The key question: who do you trust to deliver Brexit?

Little has gone to plan since then. Ms May has ditched a key election promise mid-campaign, skipped the leaders debate, and her reliance on soundbites often seems more like a crutch than message discipline.

“This is the worst Tory election campaign ever,” declared a commentator for the right-leaning Spectator magazine.

Despite it all, Ms May is still odds-on favourite to remain in her job. Unquestionably, she remains the ‘preferred PM’, as the pollsters put it.

But critics say she may to return to Downing Street a diminished figure.

Labour leader Jeremy Corbyn’s performance has surprised observers. Photo: PA

Jeremy Corbyn, Labour

The Labour leader is an old-fashioned socialist. He believes in nationalisation of industry, redistribution of wealth and unilateral nuclear disarmament.

His rise to the party leadership in 2015, after decades as a backbench rebel, was totally unexpected but delighted the party’s progressive base.

Generally, Mr Corbyn’s policies are populist. He stands for taxing the rich, stamping out corporate tax evasion, free university, more spending on health and welfare, and tackling climate change.

Before the election, he was widely viewed as a joke – a result of bland pigheadedness and inexperience or, depending who you ask, the media’s virulent personal attacks.

On the hustings, he draws huge crowds of enthusiastic young voters. Under scrutiny his grasp of policy detail has come unstuck.

The Tories have also sought to paint him as a threat to national security, pointing to meetings he held with IRA figures during ‘The Troubles’.

Following the Manchester bombing, which saw campaigning suspended, Mr Corbyn called for a re-think of UK foreign policy, arguing that interventionist policies were a factor in the rise of terrorism.

On the the key question of Brexit, many suspect he is a closet Brexiteer, despite Labour’s long-held support of Europe. With negotiations now triggered, Labour says it would preference trade access over immigration.

Tim Farron, Liberal Democrat

Until recently, the centrist, pro-Europe Liberal Democrats were the UK’s third party. But after five years in coalition government with the Conservatives they were left with a mere nine of the 650 seats in the UK’s lower house.

As the only party offering coherent opposition to Brexit, it was thought they would pick up a lot of votes from angry Remainers. Instead Lib Dems leader Tim Farron has struggled to cut through and make an impression amid scrutiny of his personal views on issues such as gay sex.

Scottish First Minister Nicola Sturgeon wants an independent Scotland. Photo: PA

Nicola Sturgeon, Scottish National Party

A few months after Scots voted against independence in 2014, the centre-left Scottish National Party won almost every UK parliamentary seat in Scotland, making them the UK’s new third party.

Then, in 2016, Scotland overwhelmingly voted to remain in the EU, and talk of another independence referendum sparked up again.

SNP leader and Scottish first minister Nicola Sturgeon has no chance of becoming British prime minister because she is not a member of the Westminster parliament.

But her party’s MPs are likely to retain most of their seats. Expect the push for Scottish independence to gather pace.

Paul Nuttall, UK Independence Party

One of Brexit’s ironies is that it led to the almost total disintegration of Britain’s answer to Pauline Hanson’s One Nation: UKIP.

Since achieving their eponymous ambition of UK independence from Europe, and the subsequent departure of combative and charismatic leader Nigel Farage, they have become politically irrelevant.

It seems unlikely they will emerge at dawn on 9 June with anything to show for themselves. Apart, of course, from their once-and-future wish: Brexit

-with reporting by Luke Henriques-Gomes