Republican presidential candidates, including, Gov. Chris Christie, have been holding mock debates, hunkering down with advisers, and finessing policy answers.

Republican candidates participate in final debate before NH primary. (Alex Wong/Getty Images)

But, their most pressing concern heading into the first debate of the primary season is one man: Donald Trump.

Some veteran political operatives suggest that the candidates ignore Trump. Others are suggesting that they confront him.

All agree, though, that Trump needs to be dealt with very carefully.