XM Satellite Radio announced Monday it has signed a multi-year content agreement with Air America Radio, making XM the exclusive satellite radio network for the left-leaning radio network. Financial terms were not disclosed. When the deal begins in May, Air America Radio will no longer air on Sirius Satellite Radio, which has 1.2 million subscribers to XM’s nearly 3.8 million.

Have you seen Left of the Dial, the excellent HBO documentary about the start-up of Air America? Painful but I could not look away.