Jo Swinson has pulled off a coup with the defection of Luciana Berger, the former Labour MP and founder-member of Change UK, to the Liberal Democrats.

It is a defection that has been a while in the making. Berger was one of the Change founders that Liberal Democrats believed – alongside Chuka Umunna and Sarah Wollaston, who have already made the journey, and Heidi Allen, who many hope will follow – would sit comfortably in the party. For Swinson, it is a validation of her argument in the campaign that she was best-placed to attract defectors: her shared WhatsApp for other MPs with babies and her cross-party work with Berger were part of what completed the transition. Berger's defection is a particular coup for the party as a whole as well.

As a symbolic victory, it sends an strong signal to Labour voters with doubts about the party that they have a new home in the Liberal Democrats. But as far as the duller, but arguably still more important currency of winning seats, the perpetual problem of minor parties in first past the post, it has the potential to achieve a breakthrough in parts of the country that the Liberal Democrats have struggled in – particularly if the rumours that Berger will seek the Liberal Democrat nomination not in Liverpool Wavertree but in Finchley and Golders Green, where she has her London home, are correct.

One of the Liberal Democrats’ perpetual problems in elections is that, with the brief exception of the aftermath of the Iraq war, they struggle to make inroads into Labour’s ethnic minority vote. The British Jewish community, like the rest of the United Kingdom’s ethnic minorities, was, until 2015 consistently more likely to vote Labour than the country as a whole. In 2010, while David Cameron was seven points ahead of Gordon Brown in the country as a whole, the two parties drew among Jewish voters

But that relationship went into sharp reverse in 2015, thanks to a combination of factors – the mayoral candidacy of Ken Livingstone in 2012, the Labour party’s changing position on Israel, and sustained and serious outreach to the Jewish and Hindu communities by David Cameron – and has been further accelerated since under Jeremy Corbyn’s leadership.

More than eight in ten Jewish voters now believe that the Labour party is antisemitic, and the party has gone from overperforming among British Jews to sharply underperforming considering the great increase in the number of social liberals, Remain voters and graduates (all well-represented in Britain’s Jewish community) voting for Labour.

That hasn’t particularly benefited the Liberal Democrats – but Change’s strongest performance (albeit from a low base) was in Finchley and Golders Green, indicating an appetite in the community for a political option other than Labour and the Conservatives.

While it is dangerous to extrapolate from pure anecdote, the impression from my own social circle is that Berger would immediately transform the Liberal Democrats’ prospects in that constituency. It’s an anecdotal impression shared by many Conservatives in the area too, who fear that it could breach the only parts of London’s Remain-y suburbs where the party is not in full retreat.

For now, it is another boost to Jo Swinson’s big argument that her party is on the up-and-up again – an argument that she will hope will carry over into the looming election.