And yesterday they kicked off their week of campaigning at Downing Street as they performed outside the prime minister's home at the Tree-Lighting Ceremony.
David Cameron, who has admitted to being a fan of the show in the past, embraced 'X Factor' fever as the trio treated the specially invited crowd to a rendition of 'Silent Night'.
Nicole Scherzinger was also there to support the boys and proudly looked on as she stood next to the PM.
The ceremony helped raise awareness for Together4ShortLives, a charity for children with life-threatening and life-limiting conditions and all those who care for them.
Following the ceremony, Christopher tweeted a picture of himself with Cameron writing: "omg! I've just switched the Christmas lights on at downing st! with Davie c! surreal xx"
The finalists are now all preparing for their homecoming gigs to drum up more support before the final.
Christopher received a hero's welcome as he arrived back in Liverpool, giving an insight into who the people who are actually voting for him are.