The Lib Dems are set to ramp up their anti-Brexit fightback after electing their first female leader by a landslide.
Jo Swinson won a ballot of 106,075 members to lead the pro-EU party - and will now face pressure to repeat a string of recent election victories across the UK.
Ms Swinson won 47,997 of the 76,429 votes cast compared to her rival Ed Davey's 28,021.
The figures suggest more than 400 ballots may have been spoilt, and more than a quarter of Lib Dems did not bother to vote.
The 39-year-old is barely half the age of Sir Vince Cable, 76, who she replaces a day before Boris Johnson is expected to win the Tories' leadership fight.
The Lib Dems were obliterated from 57 Commons seats to eight in 2015 after going into a savage austerity-pushing Coalition with the Tories - and breaking a promise not to hike university tuition fees.
But they have recently begun to regain ground, and won a sweep of EU seats two months ago with the slogan "b******s to Brexit".
Ms Swinson was the youngest MP in Parliament aged just 25 when she was elected in 2005. She was wiped out by an SNP wave in 2015 but regained her seat in 2017.
In an early protest she wore a pink T-shirt branded "I am not a token woman" and in Parliament she campaigned against over-packaged Easter eggs.
The maternity rights campaigner was responsible for bringing in shared parental leave. And she hit the headlines after Tory Party chair Brandon Lewis broke a pairing agreement which allowed her to miss a Brexit vote when she had just given birth to her second child.
But she after serving in the last one as a Business Minister and Minister for Women and Equalities.
Ms Swinson was a prominent figure in the Tory Lib-Dem coalition, and she will face an uphill battle against her legacy in government.
In February 2013 Ms Swinson joined calls by other ministers to warn that "caution" was required when increasing the minimum wage.
Ms Swinson also faced criticism in 2017 when she slammed £1,200 fees to launch employment tribunals - despite defending them while in government.
In one 2013 exchange in Parliament, she batted aside fears the fees would stop justice for new mums who'd suffered maternity discrimination, claiming they should "see the whole picture".
She said "most women" wouldn't need a tribunal anyway because "the vast majority of cases can be dealt with well outside the tribunal system."
In a second House of Commons exchange, she was asked directly if government plans would "reduce access to justice".
She replied there was "genuine concern" about fees, but MPs should remember there was also a "remission regime" - and added some cases were "vexatious and abusive".
But in 2017 she revealed: "I fought against this in the Coalition."
Ministers are expected to defend policies they disagree with under the notion of 'collective responsibility', otherwise quit or be sacked.
She had been battling it out with former Energy Secretary Sir Ed Davey and was consistently the bookies' favourite in the race.
The party has 12 MPs - bolstered by Chuka Umunna's decision to join last month - and came second in the European elections, winning 20% of the vote share.
The Lib Dems also enjoyed a surge at the local elections in response to their anti-Brexit stance.
And they are hoping to take the Welsh seat of Brecon and Radnorshire from the Tories in a by-election next week.
If the Lib Dems win the seat it will cut the new Prime Minister's working House of Commons majority from three to just two.
Ms Swinson has suggested that if Boris Johnson is committed to Brexit on October 31 with or without a deal, then the Lib Dems could be boosted even further.
She previously refused to rule out a repeat of the Coalition that saw the Lib Dems sign up to a pro-austerity, tuition-fee-hiking Tory government in 2010.
Ms Swinson told BBC Radio 4 "at the moment... I can’t envisage it" after the Conservative and Labour Parties were “dragged off to the extremes”.
Labour Party chair Ian Lavery said: “Jo Swinson sat at the top table of the coalition government and voted for vicious attacks on the most vulnerable and tax cuts for the super-rich and big businesses.
“Austerity couldn’t have happened without Liberal Democrats – leading to shocking levels of child poverty, the tripling of tuition fees, a homelessness crisis and rising food bank use."
