John McTernan is head of political practice at PSB, a strategic research consultancy. He was a speechwriter to ex-British Prime Minister Tony Blair and was communications director to former Australian Prime Minister Julia Gillard. The opinions expressed in this commentary are his own.

The French phrase for a lack of any real options is more powerful than its English equivalent -- "a plague on both your houses" -- partly because it is less familiar but mainly because it expresses such disgust.

I heard it said in focus groups before the recent French presidential election . But it really seems far more appropriate when being used to describe the UK general election , where both parties seem to have set their controls for defeat.

The Tories are likely to end up being the most surprising losers of this election. Electorally, they have been the most successful party in Western Europe since the 19th century.

They appeared to have lost their mojo when Tony Blair -- you may have heard of him -- led New Labour to three election victories in a row: 1997, 2001 and 2005.

Despite having regained the habit of winning in 2010 and 2015, the Tories, under their current leader and Prime Minister Theresa May, seem to have lost their way again.

This snap election -- which May called to deliver a mandate to push through her own vision of Brexit and give her a massive parliamentary majority, wiping out any opposition -- has misfired from the first. To start with, there was her slogan: "Strong and stable."

Clearly intended to provide a contrast with the public's perception of opposition leader Jeremy Corbyn -- who has a highly unusual history for someone running to be prime minister -- it ran into immediate problems.

Since taking over from David Cameron in the wake of the Brexit vote, May had strongly and repeatedly ruled out an early election: "I'm not going to be calling a snap election. I've been very clear that I think we need that period of time, that stability, to be able to deal with the issues that the country is facing and have that election in 2020."

While May could have got away with flip-flopping on this single issue, she had already proposed and dropped an increase in National Insurance -- a payroll tax -- in her first budget.

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Apparently not satisfied with merely damaging her "strong and stable" image, May then proceeded to torpedo it. On the day of the Tory manifesto launch, her flagship policy was a plan to shift the burden of social care for older people onto those with large property assets. It was quickly labeled a "dementia tax" by the managing editor of the Conservative-supporting Spectator magazine and former Tory speechwriter, Will Heaven.

He wasn't the only Conservative angered by the policy. It was also met with incredulity among Tory activists and hostility from Tory voters on the doorstep. Then it was dropped.

Soon after, the Tory poll lead began to drop . May's arrogant assumption that Corbyn's unpopularity with the public translated to her own popularity had backfired.

Under normal circumstances, such a catastrophic campaign would be an opportunity for an opposition party hungry for government. May is lucky that in Corbyn, she faces a man who never misses an opportunity to miss an opportunity.

Elections are won in the center, so Corbyn unhesitatingly ran as far to the left as possible. He created a clear distinction between Labour and the Conservatives with plans to hike taxes, nationalize large parts of the economy and increase public spending as far as the eye can see.

This was not so much a Labour Party manifesto as an anti-Blair one. (Corbyn has been a long-term critic of his own party's only election-winning Prime Minister in a generation.)

It appears to have had the desired effect. On current estimates, even the most optimistic polls don't put Corbyn in Downing Street. Though the manifesto went down well with his base, it is unlikely to win over the alienated white working-class voters that any Labour Party needs to win an election.

In a bizarre mirror image of May's campaign, Corbyn wanted to ensure he could not profit from her errors. To turn Michelle Obama's famous phrase on its head, when she went low, he went low.

So, having made clear he was offering tax and spend rather than economic security, Corbyn then did little to dissuade fears of his commitment to renew the Trident nuclear deterrent. This was foolish, considering one of the major Tory attack lines on him has been questioning his ability to protect national security.

The leaders of both parties have worked tirelessly to lose -- and it's likely that both still will.

May has permanently lost the authority she gained when she was the lone surviving figure after the Jacobean revenge tragedy of a Tory leadership election triggered by Cameron's resignation. Corbyn has thrown away an election that almost any other senior Labour figure could probably have won.

Faced with what columnist Iain Martin called the "worst (Conservative) general election campaign since before the war. By which I mean the First World War," Corbyn has done everything to ensure that May cannot not lose, however hard she tries.

Maybe he's seen this movie before -- he doesn't want to be the dog that catches the car. His project is to drag the Labour Party further and further to the left, not to run the country .

Where does this end? Who can tell? When does it end? That is easier to say.

Both leaders are tragically -- for country and respective parties -- unassailable. Watch this space. But you can be forgiven for watching from behind your sofa.

Ahead of the British election, we want to know: What do you think the UK's place in the world should be? Call us and leave a message. Your response could be used on CNN.