While Dougie was on IAC, a lot of the guests on the side show on ITV2, in fact the absolute majority of them, wanted Dougie to win. This included in the first week or so when Dougie was never being shown.
Reasons why? McFly have been in the music industry for 8 years now and from that they have also made a good impression on the entertainment industry as a whole.
Basically, McFly have a good reputation of being approachable and generally nice in the entertainment industry. No one would pick Harry as a favourite without him being good at dancing too of course, but I got the impression that people like Pixie Lott would pick Harry anyway from having met him several times and clearly found him nice. Westlife said Harry too, no doubt for the same reason. People like Matt Willis, one of the Sugababes, newspaper reporters etc. were all backing Dougie.
On the subject of fan votes, Danny lost Popstar to Operastar because he simply wasn't good enough. I'm very sure that Harry and Dougie have gone into each of their shows with at least enough backing to allow them to make it half way through their competitions, but they would never make it to the final on that alone. Everyone believing Harry has it in the bag now because he's a McFly boy should check out the voting figures released for I'm A Celeb. Dougie rarely topped the vote and barely made it past Mark in the last vote. If it wasn't a 2 person final he may have lost, having seemingly won over most of Fatima's voters.