Granted that is the task at hand, but Independents and disaffected democrats need to at least view him as credible. They will be his psudo club. If Trump wins it will be after an internal Republican Bloodbath.
My own close relatives who have voted democrat for 30 years are considering going republican if Trump is the nominee. So looks like there are going to be lot of Trump-democrats in 2016. Similar to Reagan-democrats in 1980.