For stories where there might be a main (focal) character AND a protag, here's from Wiki:
In any narrative
, the focal character
is the character
on whom the audience
is meant to place the majority of their interest and attention. He or she is almost always also the protagonist
of the story; however, in cases where the "focal character" and "protagonist" are separate, the focal character's emotions and ambitions are not meant to be empathized with by the audience to as high an extent as the protagonist (this is the main difference between the two character terms). The focal character is mostly created to simply be the "excitement" of the story, though not necessarily the main character about whom the audience is emotionally concerned. The focal character is, more than anyone else, "the person on whom the spotlight focuses; the center of attention; the man whose reactions dominate the screen."
So following that differentiation, in T2 Arnold would be the focal character but the audience's emotional investment lies with the protag(s), i.e. the kid and Sarah Connor. Yes, no?