Republican frontrunner Donald Trump's taunt of "sad" rival Jeb Bush -- "he was supposed to win, and he just doesn't have the energy" -- speaks volumes about the billionaire's propensity to go for the jugular. One reason Bush may not be resonating like Trump, argued veteran political observer Larry Sabato of the University of Virginia, is that Bush is among the status-quo politicians who are seen as "human tape recorders," who regurgitate consultant-approved soundbites.