Copeland has been voting Labour for more than 80 years. On Thursday many felt it was time for a change and, as in the words of one voter, "went for the blue". Why?
The nuclear question seems to have been the big one for voters the BBC spoke to.
"I went Conservative because they back nuclear," a voter called Amanda in Whitehaven told the Today programme.
"A lot of my family and friends are in the nuclear industry, the whole area depends on it."
Gavin McCue, who runs a catering equipment company, said nuclear was a "massive issue" and "there is so much at stake" around here which is why he voted Conservative for the first time.
He also said issues such as the future of Whitehaven's West Cumberland Hospital, along with getting an improved A595 link road were important.
In the end, the area's new Tory MP Trudy Harrison won with 13,748 votes to Labour's Gillian Troughton's 11,601.
Labour MP for neighbouring Barrow and Furness John Woodcock said the problem was bigger than Mr Corbyn's stance on nuclear.
He told Today: "The result is a disaster for us, we should not try and insult anyone's intelligence by suggesting it's anything but that.
"The nuclear industry was important but that was not by any means the only thing that came up on the doorstep. I hope there is a point where actually as a party we are prepared to look with clear sight at what is happening to us about our situation nationally.
"We are in trouble as a party and actually this is a time when the country really needs an effective opposition. We are not providing that at the moment.
"The position we are in at the moment we are not on course to victory [in the next general election], we are on course to an historic and catastrophic defeat which will have very serious consequences for all the communities we represent."
Mr Corbyn has called the result was "very disappointing" but has said he would not step down.
Andrew Gwynne, who led Labour's campaign in Copeland, said: "We have got a job to do to rebuild the Labour Party and policies that will connect with working communities in time for the 2020 election."
Analysis: Labour no longer Copeland establishment
By Richard Moss, political editor BBC Look North
Copeland was not a safe Labour seat - but it should have been one they held on to. Oppositions do not usually lose to governing parties.
And this also offered Labour a chance to capitalise on a key issue for the party - the NHS and concerns about the local hospital.
The failure to do that will worry the party. The Conservatives said the result was a rejection of Jeremy Corbyn and his - at best - lukewarm support for the nuclear industry.
But it is true Labour's problems have been building for a while - the area chose an independent directly-elected mayor in 2015, ending Labour control of the council.
Jeremy Corbyn has put the result down to voters feeling let down by the political establishment.
Labour used to be the establishment in Copeland. For now, that's not so certain.
Independent mayor of Copeland Mike Starkie told BBC Cumbria: "The scale of it was a shock, over the course of the night it became more apparent the Conservatives were growing in confidence, like everybody else I was surprised by how large the majority was in the end."
He said he was hopeful that Conservative pledges made during the election to increase investment in Copeland would be fulfilled.
Mr Starkie said: "During the election we have had any number of high-profile politicians in the area all making pledges, now they've got to put their money where their mouth is and back Trudy up.
"The Conservatives have taken a seat they haven't held for as long as anyone alive can remember.
"I think there will be quite a lot thrown at it where the Conservatives will try and make a point that they can make a difference."
Copeland, created in 1983, and its predecessor constituency Whitehaven have returned Labour MPs since 1935.
One Labour voter who felt it was time for a change in Copeland was Eda.
"Labour has been too long in Whitehaven ," she said, adding: "They haven't made any difference."