Leavers have put their trust in Boris Johnson. But can he really repay it?

The voters who appear to have propelled Boris Johnson back into Downing Street have not so much endorsed the Conservative party as conjured up a new party to wear the old Tory colours. There are plenty more results to come in, but the capture of Blyth Valley, Workington and Darlington by candidates in a blue rosette might well stand out as emblematic moments at the start of a grim night for Labour.

The Northumberland seat has been off limits for Conservative challengers for generations. It was protected by a 7,915 majority, yet that electoral barricade fell. Notably, the Brexit party candidate took another 3,394 votes, suggesting a voracious enough local appetite for leaving the EU to elect Johnson’s man, and have a few loose ballot papers for squandering on Nigel Farage’s also-ran candidate.

The new, post-2016 political force of Brexitism has exerted such a profound magnetic pull on traditional Labour heartland seats that the old political compasses don’t work anymore.

It is too crude to pin the whole of Labour’s collapse on its squeamish and convoluted Brexit position. Supporters of Jeremy Corbyn are emphasising that dimension, partly because it is plainly a huge factor but also out of keenness to insulate the leader personally and his economic policy prospectus from blame. In reality, everyone who visited Conservative target constituencies during the campaign identified twin problems for the opposition: impatience with the delay in enacting EU withdrawal and a quite visceral aversion to the Labour leader.

Johnson’s campaign strategy required the combined thrust of those two forces, propelling leave voters into a polling booth with the feeling that stopping Corbyn and “getting Brexit done” were part of the same imperative of national renewal. It looks from early results that it worked. The average swing from Labour to Conservative in the first three seats to declare was 8.3%. Solidly Tory seats in the south have become safer, while safe Labour ones in parts of the Midlands and the north – in Washington and Sunderland West, for example – have turned more marginal.

It should be exceptionally difficult for a long-incumbent party to achieve any movement in its favour, let alone on a lurch on the scale seen in some places tonight. The Conservatives have been in power for nine years. Labour attacked that record relentlessly during the campaign and still retreated from their electoral bastions. In over a century, no party has lost seats after spending such a long stint in opposition. The Tories have defied the normal physical properties of the political pendulum.

The implications are profound for the future of British politics, and not just because Johnson will have the leeway to govern without parliamentary impediment. His majority will be founded on the acquisition of seats containing tens of thousands of people who not long ago would never have imagined they’d have a Tory MP, let alone voting for one. His mandate is written by people who do not see themselves as typical Conservatives. They will have economic, social and cultural expectations of government that the old Tory party is ill-equipped to provide.

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The grievances and frustrations that led to strong support for Brexit in 2016 will not be satisfied by the simple fact of leaving the EU next January – although the legal fulfilment of that pledge now seems certain. While Johnson can be confident of meeting the technical requirement of “getting Brexit done”, his relationship with his new leave voters could quickly be strained by the reality of how little they will get and what will be done to them by Brexit. Deep-seated suspicion of the Conservative brand is unlikely to have been erased by the leader, even if the character called “Boris” has successfully overcome reservations that held people back from endorsing his predecessor.

There are many other currents flowing through the election. We have yet to see how millions of anti-Brexit votes have been deployed in places where the imperative was thwarting Johnson. The Liberal Democrats look like having a terrible night. Scotland’s future will be a dominant theme as the night goes on. But at this stage it seems that the prime minister’s extraordinary accomplishment is to have recruited a new electorate to his cause without having surrendered too many traditional Tory voters elsewhere.

Or, to look at it another way: the Brexit electorate has recruited a new vehicle for its interests and demands, one that wears the colours of the oldest party in British politics. It is a convenient match for now, but it will be fascinating to see how comfortable a fit it turns out to be when getting Brexit done is more than just a slogan.

• Rafael Behr is a Guardian columnist