Jamie Mallan had been the first to signal his interest in standing for the Shettleston ward, in the city's east end, after Labour stalwart George Ryan - who had held the seat for almost two decades - passed away unexpectedly earlier this month.
But his early enthusiasm to stand was not met well by friends and colleagues of Mr Ryan, with many also expressing concerns over Mr Mallan's reliability.
The local Labour Party branch will select its candidate for the December by-election tomorrow night.
The evening is now expected to be a two-horse race between Martin Neil, currently an aide to Labour MSP James Kelly, and former city councillor Irene Graham.
The SNP yesterday announced its candidate for the by-election would be 22-year-old art gallery assistant Laura Doherty.
Mr Mallan was Glasgow Labour's procedures secretary in 2011, when around 20 sitting councillors were told they would not be re-selected for the following year's local elections.
The process, in which Mr Mallan, 27, played a key role, created a split within the party on the council and the creation of a rival party in the May 2012 poll.
Questions arose about Mr Mallan's credibility after it emerged, in the middle of the process, that he ran a website pretending to be a dog called Brodie the Beagle.
One Glasgow Labour source said: "Mallan was calling and emailing people canvassing for support too soon after big George's death for a lot of people. It didn't go down well at all and he got both barrels from some for it.
"He was supposed to run the local campaign in 2012 for George and (fellow east end councillor) Frank McAveety but was given the bump after two days for not turning up. There's other stuff which would not have won him support from party bigwigs."
Mr Mallan said: "I was going to stand but have decided not to. I didn't consider it long enough to know if I could've been selected."