And given that they became the first - and still the only - group to win, that's a very good sign.
This week Rak-Su become the current favourites at odds of 6/4 to go all the way, leapfrogging long-time favourite Grace Davies into top spot.
And bookies Ladbrokes report that since their live performance last Saturday, 87% of all outright bets taken have been on the RnB group.
Alex Apati of Ladbrokes said: "It's been six years since a Group headed the X Factor outright market and we all know what happened that year, so don't be surprised to see Rak-Su being crowned winners next month.".
Tonight's show saw the four piece open the latest live show with their spin on a George Michael classic.
The performance won praise from all the judges ahead of the next elimination of the series.
Once again viewers will vote over the weekend and two more acts will be sent home.
Current X Factor odds
Rak-Su - 6/4
Grace Davies - 2/1
Kevin Davy White - 10/1
Lloyd Macey - 12/1
Holly Tandy - 16/1
Sean & Conor Price - 25/1
The CutKelvins - 25/1
Vote for your top singer of the Final 12 in our poll below...
The X Factor 2017 continues this Saturday at 8:10PM and Sunday night at 7:30PM on ITV
Guests stars performing will be One Direction's Harry Styles and Paloma Faith.
The final is scheduled for December 2 and 3.