How so?
A bit of reinforcement to the rumors of how much trouble her campaign is in. And if he gets involved and she doesn't show any significant improvement, it will likely be portrayed as "nothing can save her!" (Not that we haven't seen plenty of that already.)
Plus, as of now, she just hasn't earned a place that high up on the priority list. Others need the President's help just as badly and are more competitive in their races. If she can keep her staff together and post some better polling numbers, I think he'll be there after Labor Day. Just my two cents.