GARDAI have arrested the chief suspect in a pub close to where the attack happened.
Dad-of-one Moses Ayanwole (41) was fighting for his life today in an induced coma at St James's Hospital after the brutal assault outside Pearse Street Library at 12.20am yesterday.
The 25-year-old suspect, who is from the Pearse Street area, was not known to gardai before the incident which gardai believe stemmed from a row over a taxi fare.
He was arrested after detectives received "great help" from a number of witnesses and after CCTV footage was trawled through by officers.
Mr Ayanwole was punched in the head by a man who had sat in the taxi, and then fell heavily onto the ground as his car was parked at Pearse Street, near the junction with Erne Street.
Gardai say that only one punch was involved.
Mr Ayanwole's heartbroken wife Olusola (37) and 12-year-old son remain at his bedside as doctors battle to save him.
A shocked friend of the taxi driver, who lives at Rusheeny Grove in Clonsilla, said Moses is a "very gentle" man.
Ekundayo Ominiyi said: "He is a very easy-going guy. I have known Moses for a long time, we used to attend the same church.
"This is one of the risks of the job when you are driving a taxi. Getting hurt is a big fear."
Two passers-by who witnessed the attack called an ambulance for Mr Ayanwole, who was conscious at the time.
But the taxi driver's condition deteriorated after he was taken to St James's Hospital with serious head wounds.
Doctors decided not to transfer him to Beaumont hospital, which specialises in head injuries, as he was too ill.