Former Tory minister Rory Stewart has quit the race to be London’s mayor.
He said the “considerable challenges” of running as an independent candidate in the extended contest were “forbidding”.
“I have decided that I will not be standing again for Mayor in the now delayed 2021 election,” he tweeted.
“It has been a great privilege to work with so many amazing people with such passion and vision for London. Thank you very much again from the bottom of my heart.”
Local and mayoral elections in England had been due to take place on 7 May but it was decided in March to postpone them for 12 months because of the coronavirus pandemic.
The former Conservative leadership candidate said it had been an “agonising decision” to quit the mayoral race but said he could not ask his unpaid campaign volunteers to continue for another year.
He said: “I firmly believe London is the greatest city on earth – and it’s courageous response to COVID-19 proves that more than ever.
“It would have been the honour of my life to serve the city as mayor, but while the considerable challenges of running as an independent were manageable for a normal race they are forbidding for an extended and delayed election.”
Mr Stewart told the Evening Standard: “We were on our way to a great battle this time round, I thought. One of the team just said: It’s like one of those drag races – we built our car but we never really got to race it properly.
“It’s been a very difficult decision. It’s a job I really, really dreamed of. I don’t think I will ever find another role in the world which would be as exciting or satisfying as that. It would have been a great, great privilege. There is no city like it in the world.
“If I had been lucky enough to be elected I would much rather have done [this] than being prime minister.”
Mr Stewart had pledged to quit if he failed to cut crime as mayor, and a Come Kip With Me initiative of sleeping on Londoners’ floors to understand their problems attracted widespread coverage.
Asked why he had not delayed taking a decision until the lockdown ended, he said: “I think it would have been dishonest. I have taken a few weeks to get my head straight.
“Yes, I could have left things open and I could have teased people a bit, but I think it would have been unfair to myself or my supporters.
“A lot of our donations were very small donations. I can’t let people continue to donate on false pretences.”
The most recent opinion poll from Queen Mary University of London put him in third place on 13%, behind current mayor Sadiq Khan and Conservative candidate Shaun Bailey.
Mr Stewart, a former international development minister, quit as an MP in October to run in the mayoral contest in the capital.
A month earlier, the prominent Remainer had the whip withdrawn after voting against the government on Brexit.