Pence is the biggest asset Trump has. For him to even think of replacing him, he'd be a jerk.
It's probably the other way around. Pence is lucky to have Trump.
They're actually quite good for each other. Pence was a guy who was a prominent House conservative whose career seemed to stall, and even though he moved up to IN Governor, it didn't seem to make him more prominent. THEN . . . Trump picked him. I really wondered who'd handle the role for Trump's VP without looking phony or looking like a total lackey, but Pence has looked ggod in the role; a role he wouldn't have but for Trump. And he helps give Trump props with religious conservatives, keeping them focused on what Trump is doing, as opposed to what he's saying or Tweeting.