Former Aston Villa boss O'Neill and Mark Hughes, who left Fulham in June, were swiftly installed at the top of the bookmakers' lists after Bruce's departure was confirmed on Wednesday night.
However, while bookmakers were quoting Hughes at 4/7 favourite, Press Association Sport understands that Irishman O'Neill is the man who enjoys greater support within the boardroom at the Stadium of Light.
That news will go down well with the club's fans, many of whom have cited O'Neill's boyhood fondness for the club as an indication that he would relish the chance to take over the hot-seat for some time.
The Black Cats are keen to make a swift appointment, but know whatever decision they take must be the right one with the Barclays Premier League season already a third over and the side languishing in 16th place, just two points clear of the drop zone.
Bruce's assistant Eric Black will take charge of the side for Sunday's trip to Wolves, but it is not beyond the realms of possibility that they new man could be in post and watching from the stands if Short and the man he replaced as chairman, Niall Quinn, get their way.
O'Neill has been out of the game since leaving Villa in acrimonious circumstances in August last year, but has been linked with virtually every managerial vacancy since.
He has vast experience after launching his career with Wycombe, and his spells at Norwich and Leicester won him a chance to manage Celtic before heading south of the border once again.
Oversees candidates Carlos Queiroz and Ronald Koeman have also been linked with the job, although Sunderland are understood to want a man with Premier League experience.
They are also keen to avoid a compensation battle, so suggestions that Everton's David Moyes could be a serious contender seem wide of the mark.
Source: PA
Source: PA