The North Norfolk MP - who has spent the last two days talking his options through with family members - is among the bookies' favourites to take the helm after Tim Farron stood down saying he could not reconcile his strong Christian faith with the party leadership.
The committed Christian took the reins in 2015 after the Lib Dems' disastrous showing at the general election that year, in which they were reduced from 57 MPs to just 8, with the electorate punishing them for their part in the coalition government.
Writing for the i newspaper, the former chief secretary to the Treasury said: "You can not be a leader of a liberal party while holding fundamentally illiberal and prejudiced views which fail to respect our party's great traditions of promoting equality for all our citizens".
But his leadership was called into question after Lord Brian Paddick - the party's home affairs spokesman in the House of Lords and a well-known gay activist - said he was quitting because of the leadership's views during the election.
On Twitter, Richard Chapman, adviser to the Church of England on Parliament and politics, said what had happened to Farron was "awful". And then imagine what would lead me to voluntarily relinquish that honour.
"He increased our membership massively and he got people's enthusiasm back and brought in some decisive messages which helped us to win the by-election in Richmond Park a year ago".
At the start of this election, I found myself under scrutiny again - asked about matters to do with my faith. We had a hard election in 2015, so any ideas that we would go back to 50 MPs in 2017 was wishful thinking.
Farron's religious beliefs emerged as an issue early on in the recent British general election when he was challenged on his attitude toward same-sex marriage in a TV interview and was asked whether he thought homosexuality was a sin.More news: Pakistan can upset any team on their day, says Virat Kohli
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Mr Cooke, from Bramcote in Nottingham, admitted that he had sent an email to party bosses with a complaint about Mr Farron's personal conduct while "drunk" and has since retracted.
When he visited Hull during his tenure, she said he came across as "personable and likeable". For this, I am fired up and ready to go.
"I'm delighted to announce that I am standing to become Deputy Leader".
This is not an unreasonable point, you might say.
Ms Swinson could still end up running the party on an interim basis after Mr Farron steps down in July, if she is successful.
The 37-year-old East Dunbartonshire MP took on ex-deputy prime minister John Prescott during the 2001 general election, taking almost 15 per cent of the vote in Hull East.
Her decision leaves Sir Vince Cable, 74, the former business secretary, Sir Ed Davey, 51, the former energy secretary, and Norman Lamb, 59, the former health minister, as the frontrunners.
"The world hasn't changed", she said.