This poll is probably much more reliable than the one below.
I think Rachel has a very real chance of overturning Tom's (presumed but strongly evidenced) phone vote lead. Another factor is when they announce that Tom won the phone vote last Saturday. Will it mobilise Rachel's fans to pick up the phone?
Although Rachel was overmarked earlier in the series, her breathtaking Argentine Tango was the dance of the series and will have won a lot of fans. The released X Factor results show that people switch allegiance easily and often (I will post on this in depth soon).
Personally, I am strongly green on Betfair on Rachel and Tom so I am in an enviable position. My advice is to lay Lisa on Betfair, who has no chance at all, then watch on Saturday before betting more on the outright winner.