Interesting question, Bazile... at this point (and I am a Republican {capital "R"}) I think the interest in Trump's candidacy revolves around an overwhelming dislike and distrust of the current governing body. By that I mean, there exists, in both Party's, an elite group of professional politicians whose entire lives are devoted to one thing and that's remaining in office. Historically, the House of Representatives as well as the much later structured U.S. Senate were meant to bequote[citizen] politicians remaining in office for just one term... two or three at most.
So, what we're seeing this time around (the National Election is next November) is attraction to those that are anti-establishment... embodied by the rhetoric and personality of Donald Trump.
Every time a politician forecasts Mr. Trump's falling in the polls, his popularity goes up another notch or two, regardless of what he actually says. This is due to his ability to communicate with the commoner (even though his own wealth is measured in the billions of dollars) and his spitting in the eye of those in power.
I like some of the things I hear from him, but am reserving judgment until the voting occurs for the nominee (each State has a preliminary nominee election. Two of those will occur within the next few weeks).