In the glow of the afternoon sun on the Thames, a Liberal Democrat and an anti-Brexit campaigner stood, beaming, at the prow of a boat. George Turner, the Lib Dem candidate for Vauxhall, and Gina Miller were attempting a pastiche of an infamous shot from the EU referendum campaign, where Labour’s Vauxhall MP, Kate Hoey, sat aboard the so-called Brexit flotilla with Nigel Farage. For the resolute remainers Turner was trying to appeal to, it should have been an effective stunt.

But however ambitious the photocall, the logistics could not quite match the vision they had in mind. The boat was beached – it was in fact a bar on the waters’ edge, in contrast to the Ukip fleet that sailed past parliament chased by Bob Geldof in a rival vessel. It might be said that Turner’s campaign, too, has more ambition than serious hope: while his attempts to beat Hoey have gained attention, he may struggle against a majority of 12,000.

Pro-EU campaigner Gina Miller and Lib Dem candidate George Turner in Vauxhall last week. Photograph: Andrew Matthews/PA

When the election campaign began, such lofty goals seemed possible. The early signs looked very promising for a Lib Dem revival: a string of council victories, a byelection win for Sarah Olney in the staunchly remain Richmond Park, and a surge in membership to more than 100,000.

The Lib Dems’ campaign launch saw their leader, Tim Farron, say the party was seeking to become “the real opposition” and the voice of the 48% who voted remain in the EU referendum. A second referendum on any deal negotiated with the EU – with the option to remain – was put at the heart of the offering.

Yet throughout the campaign, the party has barely shifted its position in the national polls, hovering at the 8% mark, equal to its desultory 2015 performance that saw it reduced to just eight seats. Farron found himself fighting negative stories about his views on abortion and gay sex early in the campaign, a damaging distraction.

Farron had some eye-catching moments in the TV debates, as when he told viewers to “switch over to Bake Off” instead of watching Theresa May’s stand-in, Amber Rudd. And his interventions in the aftermath of the London Bridge terror attack – including highlighting a shelved inquiry into foreign funding of radicalisation – caught national attention. Yet, despite that, 30% of voters in the latest Ipsos Mori poll say they have “no opinion” of the Lib Dem leader.

Tim Farron exits a rescue hovercraft during a visit to Burnham-on-Sea. Photograph: Yui Mok/PA

“The problem they’ve had throughout the campaign is they have wanted Britain to realign along Brexit lines,” Joe Twyman, YouGov’s head of political and social research said. “But there are a significant proportion of remainers who think the result should be respected – so it’s now two-thirds who think it’s right we should leave.”

Nick Clegg, the former deputy prime minister, admitted that sentiment was coming up on doorsteps in his Sheffield Hallam constituency. He said: “What I hear a lot is a very British phrase: ‘Better make the best of it.’ It was such an acrimonious debate, I totally understand why people don’t want to go there.”

Farron will visit Bath over the last days of the campaign but nothing is planned for Cornwall or the rest of Somerset, including seats that the party had high hopes for, such as Yeovil and Taunton. Privately, party sources admit that the south-west is a huge challenge, given the number of Ukip voters likely to switch to the Tories. In the final weeks, the battlebus stops show a change of priorities, with Farron campaigning in Scotland, in Clegg’s Sheffield seat and in London.

Prof Glen O’Hara of Oxford Brookes University, said the Ukip vote swing to the Tories was the main problem. “Take half off the Ukip score and give it to the Conservative in each seat in Cornwall and Devon for instance, and there’s just no way the Lib Dems can scale the barricades,” he said.

Farron speaks as Nick Clegg looks on during a rally in Kingston upon Thames. Photograph: Leon Neal/Getty Images

“Their failure to fly in the local elections was a key moment. If they’d taken lots of county council seats, especially in the West Country, they would have got a lot more attention as a plausible opposition.”

The party’s candidates are also facing a tough challenge from the Tories in several seats, including Norman Lamb in North Norfolk and Tom Brake in Carshalton and Wallington.

Lamb, a former health minister in the coalition government, has stayed away from the national campaign, concentrating all his efforts on keeping his seat. One senior Lib Dem source said it was right he had been able to focus locally. “I’ve put £20 of my own money on it, we are not going to lose that seat,” the source said.

“There are micro-factors which affect each seat, which are not reflected in the national polls. God’s honest truth, we will gain seats in this election. The reason we keep returning to St Albans, Twickenham and Vauxhall is the data there looks really, really good.”

Twyman said he agreed with that analysis and said the party had a good chance in seats where local circumstances were specific, such as in St Albans and Vauxhall where the majority voted remain but where the sitting MP backed Brexit.

“In Twickenham, Bath and Cambridge, constituencies with heavy remain leanings, the poll ratings don’t preclude them from winning them,” he said.

One key Lib Dem campaign message may be undermined in the final days, however. When the Guardian hit the doorsteps in Twickenham with Vince Cable early in the campaign, almost all those who voted Tory at the last election said they had feared Ed Miliband becoming prime minister.

Tim Farron launching the Lib Dem election manifesto. Photograph: David Nash/Barcroft Images

Doorstep after doorstep, people said they would back the Lib Dems again because they had no such fear of Jeremy Corbyn winning. But with Labour surging in the polls, that demographic could start to reconsider.

“The squeeze on smaller parties is an effect of two big ideas – Brexit and Corbynism,” O’Hara said. “They’re sucking in all the oxygen.”

Clegg said the main parties both wanted to divert discussions away from the minutiae of Brexit. “May is just talking about herself ... Corbyn is talking about everything else but Brexit,” he said. “It’s not easy for anyone to disrupt that when the two larger battalions lock horns on turf which suits them and doesn’t suit anybody else. I really hope people, particularly Guardian readers, understand what is going on.”

Labour’s apparent surge could also throw some seats that the Lib Dems had banked on retaining or regaining into contention. Younger voters are thought to be behind much of the upswing, but in 76 seats where 18-24s outnumber over-65s, the two marginals are Cambridge, which the Lib Dems had hoped to regain, and Leeds North West, which they are defending.

The most promising terrain is still south-west London, where former ministers Cable and Ed Davey are standing to regain seats lost in 2015. “I’d like to be higher in the polls, but I don’t think we’re being squeezed as much as Ukip and the Greens,” said Davey.

Clegg, the party’s most recognisable public face, has been at the centre of campaign events. As well as doing a solo poster launch in Vauxhall and headlining a televised Brexit speech on Tuesday, he fronted a visit to Kingston hospital, which was punctured by the shouts from a white van driving past: “Come on Theresa!”

The party can still draw enthusiastic campaigners to most events, even to Thursday’s rally in Kingston in a near-windowless community room that felt at least 10 degrees hotter than the 25C sunshine outside. “We are in a close fight, we think we have our noses in front,” Davey said. “It’s always been close here, I won by 56 votes in 1997.”

Twyman said the Lib Dems would need to show some progress if they were to remain a viable political movement. YouGov’s research shows liberalism could still be a potent electoral force. “In the studies we’ve done, the biggest single group in this country is the progressive, internationalist, pro-EU, liberal group,” Twyman said. “That group currently votes for lots of different parties.

The dire Brexit warnings from the party are unlikely to resonate yet with voters who are feeling no ill effects, Twyman said. “Let’s say in 2019 we leave and by 2020 the economy is in the toilet ... I’m not suggesting that will happen, but that’s a brilliant position for the Lib Dems to come in and say ‘told you so.’”