There is too much time before the election and Donald Trump knows it. The more he talks the more different groups of voters he alienates and so he is getting desperate to find his niche with the most ignorant voters and hopes he can hold on. Sanders has solid support on the hand, that is actually growing.
Bernie Sanders has a great chance to beat Trump. They are polar opposites in many regards (politically correct, man of people/wealthy) and if Sanders can beat Clinton in the primaries then Sanders, in my opinion, would be able to beat Trump because, as hard as it is to admit, being a man he could steal some votes from the Republican side who do not like Trump but are too stubborn to admit a woman can be president.
Sanders is saying lots of things out of fear , but is not like that at all. Trump is actually going through this race without any type or kind of fear in his veins. Sanders has a long way to go if he wants to at least be in the finals.
Sanders most likely won't even beat Hillary Clinton. Why should we even be concerned with Sanders going against Trump yet? Sanders is a communist. While the US may be heading that direction, communism is a failed practice. Sanders will not even win the Democratic nomination. Trump is not scared of Sanders.