Jo Swinson was the first female Liberal Democrat leader to be elected after she had inflicted a devastating defeat on her challenger Sir Ed Davey.
The 39-year-old mother of two will succeed Sir Vince Cable after receiving more than 47,000 votes in the competition, while Sir Ed is a little over 28,000.
Politicians like Justice Minister David Gauke, who will resign tomorrow, have now stepped in and said that the Tory Party could lose voters to the “energetic and passionate leader”.
He also said a Brexit scenario without trade would play directly into the hands of Lib Dems.
A total of 106,000 ballots were issued in competition, with approximately 76,000 members of Lib Dem entitled to vote – a 72 percent turnout. Ms Swinson said her “top priority” as a leader would be to “stop Boris and stop Brexit”.
Ms Swinson and Sir Ed, both ministers in the coalition government, have been fighting for seven weeks for the right to lead the party after Sir Vince decided to withdraw earlier this year.
The winner of the competition becomes the leader at a high point in the recent history of Lib Dems.
According to The Times, Mr Gauke added that Ms Swinson “should not be underestimated”.
He said if the party limited its support to those in favour of a No Deal Brexit, it would be “out of contact with many people who voted for the Conservatives”.
He added: “It is important that the Conservative Party appeals to the voters in the centre.
Ms Swinson said activists after the announcement was made today: Tomorrow Boris Johnson will probably take the keys to number 10 and set us on the road to a harmful No Deal Brexit.
Stopping Boris and stopping Brexit is my top priority as a leader.
This job begins with winning the by-elections of Brecon and Radnorshire to bring Jane Dodds to parliament, cut Johnson’s wafer-thin majority and bring us one step closer to ending Brexit.
Ms Swinson stressed that “liberalism is alive and well” when she suggested that Lib Dems were best placed to counter an obvious rise in nationalism.
Faced with nationalism, populism, the Brexit disaster, the two old parties have failed,” she said.
Our group was clear about Brexit from day one.
We believe that Britain’s best future as a member of the European Union lies, and therefore, as your leader, I will do everything I can to stop Brexit.
“It is the Liberal Democrats who can drive the renewal our country needs.
She also claimed to be a “candidate for prime minister” and said that “there are no limits to my ambition for our party and our movement”.
Mrs Swinson will be the first leader of a major British political party born in the 1980s.
Sir Vince’s decision to position Lib Dems as a “Stop Brexit” party led to much better results in the local elections and then in the European Parliament elections earlier this year.
The Lib Dems finished the latter in second place overall as many of the remaining voters gave their support to the party, while the results of the local elections were the best ever.
The party has translated this ballot dynamism into a rise in Westminster’s electoral imagination, with Lib Dems even leading some polls as the Tories and the Labour Party fought.
The party’s assets have also been strengthened by the implosion of Change UK – another party that also fights for Britain’s retention in the EU – and the assault of Chuka Umunna.
The Lib Dems now have 12 MPs and are hoping for a parliamentary election as soon as possible to take advantage of the anti-Brexit sentiment.
East Dunbartonshire MEP Ms Swinson was the bookmaker’s favourite in the race, having been Sir Vince’s deputy from July 2017.
She has suggested that if Mr Johnson enters number 10 on Wednesday as expected and keeps his promise to remove Britain from the EU on 31 October with or without an agreement, the Lib Dems could let their shares rise even further.
Sir Vince will resign as leader after two years after taking over from Tim Farron following the 2017 parliamentary elections.
Sir Vince wrote to party activists in May to announce his intention to resign.
He told us the rank of the group: “There are great challenges ahead of us. One of them is to finally win the fight to stop Brexit.
Our campaigns have given hope; now we have to secure a referendum in Parliament and then win.
Another is the opportunity created by the conflict and disintegration within the two main parties to build a strong, liberal, green and social democratic force at the centre of British politics.
“We are now in an excellent position to lead such a movement.
Before the announcement of the leadership was made, Mrs Swinson paid tribute to Sir Vince.
She said: “Before we figure out who will lead Lib Dems next, I want to thank Vince Cable for everything he has done as our leader over the past two years.