Tory campaigners are confident that the party will hold Old Bexley and Sidcup – the first in a series of closely watched parliamentary byelections – as polling stations close in the suburban south London seat. Canvassers who spent the day trying to “get out the vote” said they expected the seat that has voted Conservative since 1950 to stay blue, though admitted some voters had expressed dissatisfaction with Boris Johnson. Some reported being told by residents that they would not cast a ballot, while others vowed to switch to other parties, including Labour and Reform UK. However, the local Tory campaign centre was said to be “pretty confident”. The short race began last month, after the death of James Brokenshire – a well-liked former cabinet minister who died of lung cancer. The Tories’ choice to replace him, Louie French, hopes to hold on to a large share of the vote, though Brokenshire’s 19,000 majority is likely to be slashed given that turnout is expected to be significantly lower. It was reported to be as low as 34%, according to the BBC Newsnight policy editor, Lewis Goodall. Labour sources have talked down the prospect of a shock result like that seen in Chesham and Amersham, the traditional Tory seat in Buckinghamshire that fell to the Liberal Democrats in June. After the polls closed at 10pm, the shadow solicitor general, Ellie Reeves, said: “This seat has always been a safe Tory seat, and we don’t expect that to change tonight. However, people are increasingly fed up of the prime minister’s broken promises … Patience is wearing thin with Boris Johnson. “We’ve run a positive campaign and people have been open to hearing Labour’s offer, but to win this was never within reach for us.” Keir Starmer’s party lost one of its traditional heartland seats, Hartlepool, in May, and only narrowly held on to Batley and Spen the following month. The prime minister, Boris Johnson, and other senior members of the cabinet have made appearances in Old Bexley and Sidcup in recent days, while on Thursday, Keir Starmer visited an energy facility in Easington, east Yorkshire. Labour’s candidate in Old Bexley and Sidcup, Daniel Francis, told the Guardian last week it would be an “enormous challenge” to flip the seat. Lord Hayward, a Tory elections expert, said a swing to Labour in line with its current position in the polls – which is neck and neck with the Conservatives – compared with the 2019 election result would keep the Conservatives’ vote share above 55%. He added that such a result would be “staggeringly good for a government in a byelection”. Tory MPs and aides were told to assemble for a 5am “dawn raid” – with party insiders admitting that, even though they thought they would hold the seat, the narrower the majority, the more uncomfortable questions it would raise for Johnson about his leadership. The prime minister has come under greater heat from some colleagues in recent weeks, after sparking a sleaze row, numerous U-turns and a speech to business leaders that featured meandering anecdotes about Peppa Pig World. One Tory councillor who visited the seat recently said reports the party’s voters had “weak motivation” and were “disaffected with Boris” were borne out on the doorstep. Voters the Guardian spoke to on the campaign trail called Johnson an “idiot” and “buffoon”, but complained about the lack of an effective opposition from Starmer. Polls opened at 7am and closed at 10pm, and the result is expected to be announced overnight at about 2am. The Tories may face a tougher race later this month, with the byelection to replace Conservative former cabinet minister Owen Paterson in North Shropshire on 16 December. He stood down from the Commons after being found to have committed an egregious breach of paid lobbying rules. Another byelection will be held in Southend West after the murder of Sir David Amess in October, but no date has yet been set.