The exist polls were sure as hell wrong in 2004 when South Carolina exit polls, as well as the exit polls from other states, had Kerry winning and it was not true.
They are not always right but are only RARELY wrong. And no poll ever had Kerry winning SC; you’re thinking of Ohio maybe.
The polls were also wrong on a Senate race in NH a few years back where they called it for the Rat when Bob Smith (R) really won re-election. Other than that the exit polls are almost always right.