It's a personal political journal and news "aggregator" which collects news from elsewhere and re-posts it, adds a small amount of original commentary, and exists primarily to give one or two people a place to vent and sell ad space.
It's different from a "personal blog" in the sense that it's not just some pimply 18-yr-old high schooler writing their opinion of the latest movies and whether their last Saturday night date was a hottie.
But in the wide, wide world of the internet, it only differs in degree, not category. Understand, that's nothing against Tucker Carlson; just calling a spade a freakin' shovel. :)
The term "blog" covers a lot of ground. See http://en.wikipedia.org/wiki/Blog for a pretty good discussion of the range and breadth of blogs these days.
By way of comparison, FreeRepublic is a forum, not a blog, mostly because the site owners do not post the articles and commentary -- the vast majority of FR's content is contributed by registered users.
"Founded by Tucker Carlson, a 20-year veteran of print and broadcast media, and Neil Patel, former chief policy adviser to Vice President Cheney, The Daily Caller is a 24-hour news site providing original reporting from an experienced team of professional reporters, thought-provoking commentary and breaking news."