Rock the Debates, a nonpartisan effort to open the presidential debates to all viable candidates, including independents and third-party candidates, offers some telling videos of the frontrunners responding to a question about their opinion of open debates. A visit to the site, and watching the videos they've posted so far, is well worth your time of you're as frustrated as I am at the major parties' efforts to exclude the candidates they don't like.
I'm an author, an editor, and an independent voter who was independent when independent wasn't cool. I was also purple when purple wasn't cool, but that's another story. The current story is that independent voters like me are finally making our voices heard, and make no mistake about it--our elected officials and wannabe elected officials are the ones who are listening most intently. It's a good time to be independent.