Yes, it's possible, according to John Hawks (who writes an excellent blog):
So, I can say without any doubt (if other examples had not been sufficient), it is absolutely possible to write a daily, high-profile blog and still be recognized by your colleagues as a scholar. In fact, it is possible to blog, do good research, and earn tenure at a Research I university.
It's a multi-part series, so keep checking his blog to learn the secrets of getting tenure.