It wasn’t a daily basis - it was just once - but it was a really big “once.” He was comfortably ahead until that occurred.
I haven’t found a lot of polling on that race, but it looks like from the Real Clear Politics site that it was always tight even before Mourdock’s comments, which it really shouldn’t have been. I suspect Lugar and establishment Republicans were backbiting Mourdock throughout the race and making it hard for him to gain traction.