I get it but I am sticking to my guns here taking Trump down is the only way.
Your binary mind wants to make it either/or.
It is not. Taking Trump down is part of what must done for an opponent, along with being an electable candidate beyond that. You got the first part, but then you get overload if someone brings another factor into the discussion.
1) To be elected, an opponent to Trump must take Trump down - or have someone else take Trump down.
2) To win, a candidate must then be the candidate that the voters want. There is no rule in life that says that if Trump goes down, Christie automatically becomes the next best choice.
Work with that a little bit.
Voters are going to flip through their playing cards from week to week to see if anything is good. Christie might get his 15 minutes of fame somewhere- mayber among NH voters because he has spent all his time there. Long run, he is a loser headed nowhere. He has been drifting around for years and in the end people end out finding him to be disgusting. Being from New Jersey your standards are lower so you do not see it a easily.