Mr Kent promptly left the group and announced he would run as an independent candidate.
Dr Macpherson said Mr Kent would have been deputy mayor if he had won the mayoral race.
"It was outright sabotage," Dr Macpherson said.
"Steve Chadwick retained the mayoralty with 7880 votes - I polled 5652 votes, slashing her majority from 6841 to 2228.
"Rob Kent only attracted 3006 votes, and Mark Gould 1618, but enough to split the anti-Chadwick vote and hand her another three years in office.
"Had Kent honoured his agreement with RDRR members over endorsement, he would now be facing deputy mayor," Dr Macpherson said.
But, Mr Kent said Dr Macpherson was making assumptions that his 3006 votes would have gone to him if he had not stood for mayor.
"But, sorry 3000 people said they didn't want to vote for him or for Steve, that's just statistical nonsense.
"The sad thing is Reynold didn't take advice and didn't run for council as well and I think he would have got onto council, would have been a good councillor and may have tipped the balance, but it's all conjecture.
"The people have re-elected me to continue the job I was doing.
"Initially I was not going to stand for council, but people asked me to stay and that's what I'll do.
"I guess Steve [Chadwick] is looking forward to it as much as I am and I'll be very interested in seeing how she hands out portfolios and who will chair the committees."
Mr Kent said he would be concentrating on financial issues, the library and health hub project and would "give it everything I have".
- Election progress results as at 3pm Sunday