Sir Paul performed with all the X Factor finalists
Sir Paul McCartney has said if Rage Against The Machine beats X Factor winner Joe McElderry to the Christmas number one it would be "funny".
The veteran singer, who appeared on the final of the X Factor last weekend told Sky News that if the rock band topped the chart it would "prove a point".
The gap between the two songs narrowed on Friday, sales figures showed.
McElderry's single, The Climb, is now just 9,000 sales behind Rage Against The Machine's Killing In The Name.
Earlier in the week, the Los Angeles rock band had established a 60% lead over the 18-year-old - who won the X Factor last Sunday.
A Facebook group aiming to get Rage Against The Machine to number one has attracted hundreds of thousands of members.
"Everyone expects Joe to do it," said Sir Paul.
"If he goes to number one then good luck to him. He's just some kid with a career ahead. I've got nothing against that, but it would be kind of funny if Rage Against The Machine got it because it would prove a point."
The Christmas number one will be announced on Sunday
The star said he got some great reaction from people about his performance on the X Factor.
"We got great feedback on the streets the next day. It's my claim to fame now."
X Factor judge Simon Cowell has criticised the campaign, but McElderry told BBC Breakfast that he was not taking it personally.
"I'm not really seeing it as a personal attack, because I think if any other person would have won it would have been the same case," he said.
"It's more against The X Factor than the actual winner. I would be disappointed if it's not number one - but it's out of my hands and there's nothing I can do about it and I just hope people get behind us and support us and buy the single."
He also admitted he is yet to hear the song by his chart rivals.
On Thursday, Rage Against The Machine appeared on BBC 5 live and band singer Zack de la Rocha swore four times during their live performance of their song.
A BBC spokesman said: "We had spoken to the band repeatedly beforehand and they had agreed not to swear."
He added: "When they did, we faded the band out and said sorry immediately.
"We apologise again to anyone who was offended."
Guitarist Tom Morello said the internet campaign "tapped into the silent majority of the people in the UK who are tired of being spoon-fed one schmaltzy ballad after another".
Some of the proceeds made from the single will be donated to a UK-based music charity.
The official Christmas number one will be announced on Sunday.