It's easy to go with Button since he's the one currently listed in second, but there's still five grands prix remaining for a total of 125 potential points which could be spread any number of ways amongst the top drivers while Button is only a single point ahead of Alonso, three ahead of Webber, and seventeen ahead of Hamilton. Button is still only second-best to his teammate, and holds more points than Hamilton not by his own skill but as a result of Hamilton's over-aggression. If Lewis would simply play it more conservatively with the overtaking, he'd come back out ahead of Button on that alone because he otherwise pretty consistently outdrives Button.
Button is just a frog's hair ahead of Alonso, who is arguably better than Button and still has a solid car under him. He might possibly be better than Webber but Webber has the better car. Then there's Hamilton, who has the same car but more skill. Any of these three could very well come back out on top of Button within the next five races, and really they should be out ahead of Button for different reasons. While it's basically just a matter of belief and opinion as to which one is better than the next, what isn't debatable is that Button is in no way guaranteed second place by any stretch of the imagination. A race or two from now he could be fourth or even fifth, depending on how things go.