David Frum got an enormous amount of attention for his blog post arguing that Republicans erred by refusing to engage with Democratic moderates on health care reform. Now he's resigned from the American Enterprise Institute. It doesn't look all that voluntary:

I have been a resident fellow at the American Enterprise Institute since 2003. At lunch today, AEI President Arthur Brooks and I came to a termination of that relationship.

Below is the text of my letter of resignation.