The Liberal Democrats may have brought confetti canons to their manifesto launch, but they have still struggled to get as much attention today as they hoped, given Boris Johnson's loose lips on the National Insurance threshold cut. They are also - by leader Jo Swinson's own admission - suffering a squeeze in the polls.

The latest YouGov poll has the party on 15 per cent, trailing Labour which is on 30 per cent and the Tories on 42 per cent. Perhaps more worryingly, given the focus on Swinson herself, voters don't seem to warm to her the more they find out about her. What's going wrong?

One of the main problems might be that the party has miscalculated what its strongest selling points are. The campaign is heavily focused on two things: Swinson and the stop Brexit pledge. It is hard to move for massive pictures of the Lib Dem leader, whether on the battle bus or in party documents and today's manifesto was branded 'Jo Swinson's plan for Britain's future'. Party political broadcasts have similarly heavily focused on Swinson. Yet it's not just the polls that suggest this may have been a mistake. I was recently surprised by conversations I had with a group of pro-Remain, and generally sympathetic to the Lib Dem voters in key target seats including Putney and Twickenham who named Swinson herself as a problem. A couple went so far as to call her an 'extremist' because of her pledge to revoke Article 50, a description that is at odds with the party's efforts to depict her as the only reasonable person in British politics.

It is perhaps difficult for those working on the party's campaign to fully appreciate this. Many of them have quite an emotional connection to Swinson, having effectively watched her grow up in the party. There is footage of a very young and earnest-looking Swinson speaking at Lib Dem conferences that activists and party campaigners remember well. The Lib Dems bear the greatest resemblance to a family or perhaps a local church out of all the parties, and you simply do not find this fondness in the other parties, regardless of the ongoing slavish admiration from some Labour activists for Jeremy Corbyn, or the excitement that Boris Johnson generates in his party conference hall. Many of the staffers on this election campaign - with the exception of workers such as deputy director of campaigns Denise Baron, who has worked in the US for the Democrats - are old hands in the party, which certainly helps them understand its bizarre structures, but also means they may not have the perspective of the kind of voters they actually need to attract.

The Article 50 pledge was also formulated during a much more chaotic time in the Brexit process, when it didn't appear that there was going to be a deal, and when parliament was deadlocked. Now that there is a deal on offer, it may be that voters feel the Lib Dems have gone over the top with this commitment, even though it relies on the party winning a majority.

There have also been strange decisions in individual seats which may send the wrong message out nationally. Activists were astounded by the party's refusal to stand down against ex-Tory David Gauke when he announced he was running as an independent. It underlined that the Liberal Democrats are no longer pitching to be a reasonable alternative to the Conservative party after it ejected the sort of MPs that its target voters like. It suggested that they had read the result of the European elections as being a sign that voters are looking for Brexit purity in a general election, rather than mere reasonableness in contrast to the two main parties.

There is, I understand, a recognition internally that the campaign needs to move on from merely producing massive posters of Swinson's face. There is likely to be a shift in advertising and messaging over the next few days. Swinson also notably refused to answer repeated questions this afternoon on whether she would block either the Tories or Labour forming a government if they offered a second EU referendum. There's a difference between giving votes to prop up a government, and refraining from voting against that government, i.e. abstaining on a Queen's Speech so that the party could get its legislative programme approved.

Now is the time to have a campaign wobble. The Lib Dems in 2015 didn't realise that their foundations weren't so much wobbling as collapsing until the last minute, when it turned out that the Tories had been mining under their support in South West seats. Their manifesto is the first major one to come out, and tomorrow's Labour launch and the chance of the Tories running out of new announcements by the time they publish theirs could lead to this whole campaign going topsy turvy. But the Lib Dems know that right now, they don't have the momentum they'd expected.