This up-to-date data, from a Republican media-buying source watching the race closely, illustrates just how little the candidates get from their biggest expense, TV ads. There is an exception to this: Negative television advertising did real damage to Rick Perry and to Newt Gingrich. But positive advertising seems to have made little dent.
- U.S. Republican presidential candidates will debate Saturday at 9 p.m. ET on CBS for the first time since Donald Trump's win in New Hampshire.
- Up to 150,000 penguins may have been killed by an iceberg blocking their access to the sea.
- And how well do you know what happened in the news this week? Take our quiz.