Many Republicans were hoping in 2012 that Gen. David Petraeus would retire and seek the GOP nomination to challenge President Obama, thinking he'd be a sure winner.

The big problem with that hope — other than the fact Petraeus wasn't interested, of course — is that no one was really sure the general was a Republican.

Now we have a strong indication he may not be, from "HRC," a new biography of former Secretary of State Hillary Clinton.

Petraeus tells authors Jonathan Allen and Amie Parnes that Clinton would "make a tremendous president" and lavishes so much praise on her that ABC's Jonathan Karl suggests he "seems to be endorsing her as a candidate for president."

Karl reports that the biggest reason for Petraeus' glowing assessment is Clinton's performance as secretary during and after the Sept. 11, 2012, attacks on U.S. diplomatic facilities in Benghazi.

Prediction: After this, Petraeus may still look like a winner, but not to Republicans.