This is about Trump's business arrangements. Other candidates subordinate their personal business interests when they run for President.
Even Hillary Clinton resigned from the Clinton Foundation board when she announced her campaign.
So far, all I've seen from Trump is personal attacks on private citizens, a lawsuit filed to preserve a personal business interest, and populist comments that have already been said by much more conservative candidates.
The Donald is finding out, if he didn't know already, that you can get away with a lot in today's culture... but running for high office as a Republican is just crossing the line.