In a post to his Frum Forum blog yesterday, former Bush speechwriter David Frum announced that his position with the conservative think tank American Enterprise Institute had been “terminated,” adding that it was an “abrupt and unexpected conclusion.”

Frum had stated days before in a much-circulated blog post that conservatives and the GOP had suffered a “crushing legislative defeat” with the passage of health care reform legislation, and blamed it on the movement and the party themselves. According to Frum, they should have negotiated with the Democrats in good faith and tried to make a deal, but were “trapped” because “Conservative talkers on Fox and talk radio had whipped the Republican voting base into such a frenzy that deal-making was rendered impossible.”

Frum followed up his “Waterloo” blog post with an appearance on ABC's Nightline, in which he stated that “Republicans originally thought that Fox worked for us, and now we are discovering we work for Fox.”

This morning, Politico's Mike Allen reports Frum's explanation for his “axing” is pressure from AEI donors:

EXCLUSIVE: David Frum told us last night that he believes his axing from his $100,000-a-year “resident scholar” gig at the conservative American Enterprise Institute was related to DONOR PRESSURE following his viral blog post arguing Republicans had suffered a devastating, generational “Waterloo” in their loss to President Obama on health reform. “There's a lot about the story I don't really understand,” Frum said from his iPhone. “But the core of the story is the kind of economic pressure that intellectual conservatives are under. AEI represents the best of the conservative world. [AEI President] Arthur Brooks is a brilliant man, and his books are fantastic. But the elite isn't leading anymore. It's trapped. Partly because of the desperate economic situation in the country, what were once the leading institutions of conservatism are constrained. I think Arthur took no pleasure in this. I think he was embarrassed. I think he would have avoided it if he possibly could, but he couldn't.”