I just caught part of his remarks on Trump last week, so I can't explain everything that led to this. But I know he discussed Trump for a while and some listeners thought Rush failed to point out some of Trumps liberal ideas, or campaign contributions to libs, etc. Rush caught a lot of email flack so he asked Trump to come on and explain some of his views and past contributions to candidates.
A guy called in complaining about Trump’s cpac speech and pointed out all the money he gives to dems and the fact several years ago he claimed to be a dem . Rush was rather soft on Trump and told the caller he would see if Trump would come on the show . Should be interesting :-)