Mayoral candidate Roger Caranci thanked his family and volunteers as he pulled out of the race and publicly announced he would support Paul Cheng to be London's next mayor.

"As of today, I have instructed my staff to shut down my campaign...Sometimes you have to do what's better for the City of London, not for yourself."

Cheng responded "I accept [Caranci's] graciousness and we will fight on to make sure London is pro-business. I want to get London back working again and I want to cut the red tape out of city hall."

The announcement comes after new poll numbers that saw candidate Matt Brown and Cheng battling to be the front-runner.

The poll done by Forum Research for the London Free Press showed Brown with 35 per cent support and Cheng with 27 per cent, a big gain for Cheng in the last couple of weeks.

Roger Caranci and Joe Swan were each at six per cent support with about 18 per cent of voters undecided.

As for Swan, he says "We're not throwing in the towel. Our message is strong, so we're doing the best we can for London...experience counts and it's not over 'til it's over."

Caranci's withdrawal from the race likely means Cheng will pick up support from the development sector and those looking for a candidate not associated with the last four chaotic years on city council.

Still, Cheng will need to convince undecided voters that he is the best choice if he is to gain enough support to win.