Let’s not over-complicate things. Prime ministers only call an early election if they need to or because they’re sure they’re going to win. In Theresa May’s case, both things apply – and in spades.

May could probably have made it through the Brexit negotiation process with the relatively small parliamentary majority she currently enjoys. It’s just that “enjoys” is hardly the right word.

The Conservative parliamentary party contains dozens of Eurosceptic ultras who have been campaigning for years, even decades, to leave the EU – and they want a Brexit that is as total as it is final. Whereas most Tories will regard the trade-offs that a relatively pragmatic PM is bound to want to make as sensible compromises, the Eurosceptics will see them as betrayals.

Obviously, a bit of sound and fury from May’s backbenches might occasionally come in handy. Other heads of government know all too well that, ultimately, any deal a politician hopes to bring home from Brussels has to be one that they can get through their own party and parliament.

But there are limits. Given May’s current majority, Tory troublemakers could have the whip hand, exercising an influence – even a veto – that goes way beyond the number of voters they actually represent. True, 52 per cent of British people opted to leave the EU. But only a minority of them were voting for the hardest of hard Brexits. Why, then, should the majority of Conservative MPs, who reflect the “have our cake and eat it” views of most Leavers (border controls, but free trade and movement too), be held to ransom by their fanatical colleagues?

By calling an election that looks set to result in a larger majority, May will bag herself a crop of first-time Tory MPs who, whatever their views on Europe, will owe a debt of loyalty to her (at least while they still have hopes of preferment and promotion). If and when things get sticky, she should be able to rely on these newcomers to see her through, irrespective of any resistance put up by the old-school ultras.

None of this means, incidentally, that Britain isn’t heading for a hard Brexit in the sense of leaving the single market (and, indeed, the customs union) because of May’s opposition to freedom of movement and the European Court of Justice. But, on balance, that hard Brexit may well be softer than it might otherwise have been – a deal mitigated by complex derogations, multiple side-deals, and extended transition periods.

None of this, of course, can be guaranteed. A multi-governmental, multi-level process might fly apart for a million and one reasons that no one can yet foresee. What we can predict with some confidence, however, is that, barring May shooting a puppy or drowning a kitten on live TV, the Conservatives are going to win a thumping great victory on June 8.

Labour’s membership elected a throwback to the 1970s who voters cannot take seriously and who struggles to get his message across, and to get it straight

It’s not just the Tories’ 20-point-plus lead over Labour in a whole host of recent opinion polls that leads inexorably to that conclusion. It’s the numbers behind those numbers.

Britain, like many other advanced democracies, has left behind the era of position politics, where tribal voters clashed over big ideas and sharply contrasting collective interests. It has moved into an era of valence politics, where what matters to most people is whether the parties competing for their support can run the country competently, as well as handle anything unexpected that may come up in the future. Not surprisingly, given this, and the fact that most people don’t have the time and the inclination to pay too much attention to policy detail, leadership matters – a lot.

Dig deeper into the polling and it becomes clear that the Conservatives have huge leads on “best party to handle” virtually every issue bar health (always a bit of an Achilles heel for them). Moreover, they are far more trusted on the economy and public finances than their Labour counterparts. On top of that, Theresa May is way ahead of Labour’s leader, not just on “preferred prime minister” but on a whole series of character traits associated with being able to do that job. With these kinds of numbers, it’s not just that May can’t lose; it’s that she can’t fail to win big.

Just as importantly, right now is about as good as it will ever get for her. Public confidence in a low-wage, low-productivity, import-dependent economy currently ticking along mainly on the back of a world-class financial services sector, largely debt-fuelled private consumption and a drastic fall in the exchange rate is only going to last so long, especially if inflation begins to kick in.

Likewise, the British public’s patience with a badly underfunded health service and a care system in crisis will eventually run out . And sooner or later, of course, at least some Leave voters will wake up to the fact that Brexit can’t possibly deliver all the goodies they were promised during last summer’s referendum: free trade deals with the rest of the world will be a long time coming, if they come at all; additional millions for the NHS won’t magically materialise; and immigration won’t fall to anything like the levels hoped for.

So May is surfing a wave before the tide goes out. The Labour Party, meanwhile, is drowning. It’s not all Jeremy Corbyn’s fault. Under Ed Miliband, the party found itself badly torn between apologising for “failing to fix the roof when the sun was shining” (as George Osborne – remember him? – used to put it) and defending New Labour’s otherwise impressive record.

Its ambivalence and embarrassment about its own rightward shift on both welfare and immigration also prevented it from communicating that shift to voters who were increasingly concerned about cultural as much as economic issues.

But if things were bad before Corbyn took over as leader, he has made them much worse – and not just by shifting Labour’s stance back to the progressive liberalism that alienates so many of the party’s potential voters and makes it such a tempting target for Britain’s overwhelmingly right-wing print media.

After its second defeat on the trot in 2015, Labour needed a forward-thinking, attractive and competent leader to take on the Tories and help win the EU referendum. Instead, its membership elected a throwback to the 1970s who voters cannot take seriously and who struggles not just to get his message across but to get it straight in the first place. No wonder the Liberal Democrats, who at least know where they stand on Brexit, seem set to make something of a comeback. And no wonder the SNP expects to hold the vast majority of the sweeping gains it made in 2015.

One “minor party”, however, isn’t looking forward to an early election. Since she became prime minister last July, almost everything Theresa May has said and done – on Brexit, on grammar schools, on immigration – has been done with one eye on bursting Ukip’s bubble. It has worked. On Thursday, Ukip’s former leader Nigel Farage announced that he would not even be standing in this election.

Whether, though, May’s embrace of right-wing populism will do her, her party, or indeed the country any good in the long term, who can tell? As the ancient Greek historian Polybius once observed: “There are far more people who know how to win than know how to make proper use of their victories.”