>>10For republicans, they'll have to rely on Trump to win: gamergaters, MRAs, anti-feminists, alt-right, Christian right-wing,conservatives, libertarians, etc.
However if Trump alienates any segment, there will be not enough support and "Never Trumpers"/Centrist Republicans will steal a sizeble chunk of vote.
Both sides will be using smear campaigns highlighting some controversial views(favored by one side and hated by other) that would split the vote.
Suppose we have a left-wing John Smith, who wants reforms/social safety nets, but harbors some mild anti-feminist views, hears that Democrats nominated Spanish-speaking feminist wants to legislate some feminism(ban sex dolls, hentai,misogynist video games,porn,online trolling,etc) he will start to doubt his commitment to the cause and will vote third-party or not at all. The perception of left-wing removing freedoms and adding bureaucracy can be very costly vs pro-libertarian candidates(that why its most popular third party in US).