turncoat

One who traitorously switches allegiance.

One who “turns his coat”—that is, forsakes his party or principles.

One who forsakes his party or his principles; a renegade; an apostate; a defector to the enemy.

A traitor; one who turns against a previous affiliation or allegiance.

a disloyal person who betrays or deserts his cause or religion or political party or friend etc.