A group of House Republicans has received a mysterious threat in recent weeks: an anonymous email that promises political retribution for those who vote yes to a debt-limit increase — sent to their closely guarded personal email addresses.

Because of the near-secret nature of lawmakers’ internal email addresses, the emails have raised more than a few eyebrows — and the possibility that one of their own was behind, or at least assisting in the attacks. …

“It’s got to be another member. Probably one of the crazy ones,” said a Republican who had seen the email, which was sent from an anonymous email address, [email protected].

In the email. the lawmakers received a set of forwarded emails sent by “unrepresentative one” to Oklahoma Rep. James Lankford and Speaker John Boehner. The apparent message to GOP House members: If you vote for a debt-limit increase, an outside group mentioned in the email will mobilize against you.