This according to a story at Politico.com. Link This can only mean he is running out of money, or he feels confident of picking up some more delegates here without the ads.  With two second place finishes and winning Wyoming, he is currently leading the pack in number of delegates, and in the end game, that's what really counts.
Although the members of u4prez don't really appear to be to passionate in their support for him, he is clearly nationally in the hunt.