Voters go to the polls today in the Peterborough by-election amid predictions that Nigel Farage’s Brexit Party will pick up their first ever House of Commons seat.

Following the new party’s success in the European parliamentary elections, the by-election - prompted by the recall of former Labour MP Fiona Onasanya - is viewed as a litmus test for the Eurosceptic group’s ability to win seats in Parliament under the UK’s first-past-the-post system.

Peterborough has oscillated between the two main parties for more than a century, with Labour winning the seat from the Tories in 2017 by a majority of just 607. But with both Labour and the Tories now in decline and the country ever more divided along Leave and Remain lines, pundits are tipping the Brexit Party to claim victory this time around.

However, a Brexit Party insider told Politico’s Jack Blanchard that they anticipate finishing a “good second” to Labour. The party appears to be trying to dampen expectations, but “in truth, anything other than a win will now be a setback to the momentum Farage has built up”, says Blanchard.

The party leader will be in Peterborough today, ahead of tonight’s result. Meanwhile, Brexit Party candidate Mike Greene has told The Daily Telegraph that he is “confident” but “not complacent”.

A successful local businessman who switched from the Tories to the Brexit Party earlier this year, Greene says: “Being Labour or Tory is a bit like supporting the same failing football team. You try to keep on hoping, but then you lose hope and realise you can’t do it any more.”

Labour have not quite given up hope just yet, though. Their belief “is Remain supporters who voted Lib Dem or Green in protest in last month’s EU election will ‘come home’ to try to block a Brexit Party win, while the Brexiteer vote is split”, says Blanchard.

A local Labour Party source tells The Guardian’s Peter Walker that the contest look “very, very close”, adding: “For us, it’s all about the get-out-the-vote operation. Our vote seems to be there, but we need to get people out, and that can be tough in a by-election.”

A win for the Brexit Party could have wide-ranging repercussions for both of the main parties. The Conservatives had been confident of taking back the seat after Onasanya was convicted of perverting the course of justice last year. Yet the Tories’ dismal showing in last month’s European parliamentary elections has spooked the party.

And a victory today for the nascent Brexit Party - which has already attracted huge numbers of disgruntled Tory voters since forming in February - could further precipitate the Conservatives’ lurch to the right.

It would also boost the chances of hard-line Brexiteers jostling for the Tory leadership. The Financial Times reports that Boris Johnson’s road to Downing Street “runs through Peterborough” today. Former chief whip Andrew Mitchell tells the paper: “If the Brexit Party win in Peterborough, it will give the campaign for Boris monkey glands.”

Yet last-ditch efforts by both main parties could prove in vain, with bookmakers anointing Greene the odds-on favourite to take the Cambridgeshire seat.

“Perhaps if Labour – or even the Conservatives, who should be the main challenger in Peterborough – had its own positive message to sell, voters might consider them as a serious option,” says The Daily Telegraph’s Tom Harris.

“But both main parties are giving the firm impression of being unfit for purpose at this crucial point in our country’s history. The Brexit Party may not triumph. But by now, most voters will have concluded that neither Labour nor the Conservatives deserve to either.”