To Carter's credit, he orchestrated the Camp David Peace Accords that not only led to a real and binding armistice between Eqypt and Israel, but perhaps more importantly turned Egypt into a US-dependent ally. Not only did Egypt turn its back on decades of foreign aid from the Soviets, their flip-flop forever fractured the united Arab front against Israel. This achievement alone recuses him from the bottom 10-15 presidents.

Also, the legislation Reagan got through Congress to deregulate oil and natural gas prices was originally Carter's bill, not to mention it was Nixon who instituted the original price fixing. In other words, conservative historians have seen fit to blame Carter for something Nixon caused and unduly give Reagan all the credit for fixing it. (Granted, Reagan deserves much of the credit. Carter's inability to influence a Democratic-controlled Congress--something at which Reagan was more effectual even as a Republican--was pathetic.)

Like I said, a mid-lister: somewhere in the 20s.