Ah got it. Since I thought it was guys like Fred Thompson that were being dismissed in the original post (Fred has an ACU rating of 86, which means 14% of the time he’s not a conservative), I assumed a new face was coming like Tom Coburn or someone like that.
No, that means that 14% of the time the ACU disagreed with his vote. While ACU ratings are meaningful, they are not gospel.
ACU ratings are not all they’re cracked up to be. A “conservative” bill might well be anti-Constitution or anti-Federalism, and someone like Fred might vote against it.