The only reason that Sanders polls better than Trump is that Republicans are holding back the information they have on Sanders' past history in hopes he is nominated. There are reasons Republicans have never stopped attacking Clinton and have not laid a glove on Sanders, and it isn't because he is Saint Bernie. If he is nominated they will spend hundreds of millions of Koch Brothers dollars telling Americans that Sanders supported the Iranian government in 1980 while the Iranian mullahs were holding Americans hostage.  They will tell us all about his support for completely removing funding for American defense. That was part of the platform of his party, the Socialist Workers Party. He was an Elector for the SWP that year. They will tell us about all his wacky theories others have referenced, but it is his past as an active revolutionary trying to undermine the US as we know it that will doom his candidacy.