To answer the original question, I think some more traditional Republicans could have been competitive; even some of the candidates would have been, despite the fact that the field was really shitty this time around.
Beyond the email leaks and all that jazz, any opponent would have had three advantages: first, it's hard for a party to win the White House three times in a row; second, the party was clearly splintered and Bernie supporters were butthurt and weren't ready to vote for Clinton en masse; and lastly, there was Clinton herself, who (love or hate her) used to be a formidable campaigner, came across like a tired, old grandmother, who's starting to show signs of dementia.
No, America would not elect a senile Socialist, regardless of what Generation Snowflake thinks..
A lot of people said America wouldn't elect a twice-divorced septuagenarian former casino owner, with a bad spray-on tan and no government experience at all... and yet, here we are.
Both Trump and Sanders saw something that the others didn't, and both succeeded in tapping it. Both were "insurgent" candidates in a sense.
One lost because the party elders had already decided to nominate a deeply flawed candidate on account of her genitals and having paid her dues.
One won because his opponents never quite took him seriously and didn't figure out, until it was way too late, that he had thrown the rulebook away.
Either way, both Donald Trump and Bernie Sanders sent a really loud message to their respective parties. It will be interesting to see what the parties learned, and what happens in the midterms. I suspect more of the same, if the reactions of the Democrats and their precious little supporters so far are any indication.
Beyond that, Trump, love or hate him, redefined political campaigning - it remains to be seen if it will last. It may be difficult for anyone but Trump to follow the Trump rulebook (especially since the only rule in it is "there are no rules" and politicos don't like that) but who knows? Politicians are definitive proof of the theory of evolution and natural selection.
One thing is for sure, the 2020 elections (and to a lesser degree, the 2018 midterms) will be very interesting.
