It can't be flat victories, or LSM would have a big lead and would always win due to most matches in the game involving them. It might be a winning percentage, or something, though.
Of course, I should have considered that. I still wonder if it's based on matches won, or territories held. Personally, I hope it's territories held, since the Influence Bar is already based on matches won.
Could also be that it takes into account how many players each faction has or how many matches they play. Otherwise, I don't see Ork and Eldar keeping up(and Orks being first for some time) with our smaller player(and thus match) numbers.
If the campaign have done something, it's to increase player numbers it seems. More players online now, which is good.
I would imagine it's territories held. Based on the snapshot of the map I had a glance at last night before bed, LSM had lost a bit of ground to everyone, with Orks holding the most against the other factions relatively, CSM just behind. That matches the numbers @Kuche put up.