The coveted title of Christmas number one single will be announced later, with the smart money on the Hillsborough charity single to take the prize.
Sales of the Justice Collective's version of The Hollies' hit He Ain't Heavy - He's My Brother edged ahead of X Factor winner James Arthur earlier in the week.
By Friday it had sold 15% more than its nearest rival, Arthur's version of Impossible, said the Official Charts Company in its final sales bulletin before tonight's chart rundown.
The Hillsborough track, which features names such as Robbie Williams, Sir Paul McCartney and Spice Girl Mel C, is being sold to help cover the legal costs of the families of the 96 victims of the 1989 stadium disaster.
Williams also has a single out but he asked fans to buy the Hillsborough single instead of his, called Different, when he realised they would clash.
On Wednesday, Chancellor George Osborne said that he will give the fund the VAT on sales of the Hillsborough single, "ensuring that as much money as possible goes towards helping these families".
The Official Charts Company's managing director Martin Talbot said on Friday that the momentum was in favour of the Justice Collective.
But he warned that they "have opened up their lead in just two days - it could easily be closed over the next two days".
The Official Charts Company said: "Given the large sales volumes of the top two singles, other tracks which have been tipped as Christmas Number 1 contenders may now be out of the running."
Those include Psy's mega-selling international smash Gangnam Style and another internet hit, the £1 Fish Man by East End market trader Shahid Nazir which went viral in the summer.
YouTube blogger Alex Day, who gate-crashed the Official Christmas Singles Chart Top 5 last year, is in the chart with Stupid Stupid.
The Pogues and Kirsty McColl's enduring hit Fairytale Of New York also features. It has re-entered the Official Christmas Singles Chart Top 20 every year for the past seven years.
The Eddie Stobart Truckers also look set to enter the Official Singles Chart Top 40 on Sunday with their re-working of The 12 Days Of Christmas.
Since 2002 the Christmas number one has been dominated by reality TV contests which end just in time for the winner to release a single.
The trend began with Popstars: The Rivals but since 2005 winners of The X Factor have topped the Christmas chart five times.
The pattern was broken in 2009 when an internet campaign saw Rage Against The Machine's single Killing In The Name outselling Joe McElderry.
X Factor winner Matt Cardle was top in 2010 and in 2011 The Choir winners Military Wives were number one.
The Official Christmas Number 1 will be revealed on BBC Radio 1's Official Chart Show later and the full Top 100 will be published on www.officialcharts.com .