While Trump is claiming he is now unleashed from I am not sure what (is it from even a pretense of being Presidential; is from feeling able to criticize everyone no matter race, gender or party?), in reality it is Republicans who are to blame for unleashing him — but it started a long time ago. Certainly, when the party leaders didn’t shut down and repudiate the birther campaign, they allowed Trump to sniff the PR he could receive by playing at politics.
Then, last year, he decided to launch his political campaign and the party leadership and individual candidates allowed Trump to be taken as a serious/real candidate.They seemed to almost enjoy the reflected celebrity of the Apprentice Candidate. If, at the onset, they (someone/any of them) had correctly positioned Trump as an intemperate,entitled frat boy , Daddy funded and bailed-out-by-twice (once by massive inheritance),unsuccessful (per recent NYTimes analyses of totality of his ventures)business person — he would not have gotten traction. Their mistake was thinking that primary voters could tell the difference between a reality authoritarian role and reality.
The lesson for the future — for Democrats as well as Republicans— is that the parties, and the country, have a stake in having reputable/respected/respectable candidates. They should not rig the systems for established politicians and office holders (as they both are to an extent now), but they should have requirements to participate in any debates. These should, at a minimum, include releasing recent income tax forms,transcripts of any recent speeches, and declarations of no conflicts of interest. Probably also a good idea to require them not to say anything stupid when they think they are in private….