She describes his dream as a political chimera.
something imagined, but not possible — often an idea requiring an impossible combination
As a proper noun Chimera refers to a fire-breathing monster in Greek mythology. It is a female monster with a lion’s head, a goat’s body, and a serpent’s tail.
More rarely, in biology, a chimera is an organism that contains cells or tissues with a different genotype.
Chimaera is also an acceptable spelling and the name of a type of fish.