The following quote is from a transcript of NBC Meet the Press interview talking about president Trump that he wanted to turn over the vote result:
And, you know, we've heard from a number of officials that the president is not necessarily fully dug-in privately on his belief that this is something that he can actually turn around. But he's fundraising off of this.
Could anybody tell me (1) the meaning of "dug-in" and (2) the usage of "off" here? I'm a English beginner, and it would be greatly helpful if you give me a little more details.