Inside of `__new__`, why is `cls` required instead of `args[0]`?

Question

I have two almost identical implementations of the __new__ method for a class.

However, in one case, there is an error message.

In the other case, it works fine.

class Klass1():
    # causes RuntimeError: super(): no arguments
    def __new__(*args):
        obj = super().__new__(args[0])
        return obj

class Klass2():
    # This code here works just fine   
    def __new__(cls, *args):
        obj = super().__new__(cls)
        return obj

instance1 = Klass1()
instance2 = Klass2()

Why would it matter whether we write cls or args[0]?

What is causing the RuntimeError exception to be raised?