"esa persona es de mi cuerda" or "no es de mi cuerda" means that person does (or does not) think like me, in a pollitical, religious, style, etc context.
Invention:Thought like two cords of alpinist, the red austrian team and the blue british team.
The people of the same "cord" are supposed to be alike/similar, not necessary exactly the same.
Example:
A: A quién piensas que votará C ? Obama ó McCain?
B: Creo que a McCain. Es de la cuerda de Palin.
So B thinks that C would vote McCain because C "thinks" or "looks like" a Palin supporter.
Web examples:
first google for "no es de mi cuerda"
"El arte cerebral elaborado en frío, en base de técnicas rígidas y fórmulas hechas, no es de mi cuerda."
"The cold, brainy art, with formal technics and rules, it's not my cord"
He places himself as a creative, chaotic person (in the other cord)
other
"CREO QUE JULIO ANGUITA QUE POR CIERTO NO ES DE MI CUERDA"
"I think that Julio Anguita, who is not in my cord...."
He is taking about a politician (communist, to simplify) saying first that he doesn't identify with him.
It's often so done in order to apear more neutral.
Saludos