Please keep in mind that my comments are narrowly focused on Trumps' convention speech. As I noted before conventions are basically "preaching to the choir"; they are usually only watched by those who strongly support the candidate and only sway unaffiliated voters when something drastically goes wrong. The post convention polling "bounces" are short term and nearly meaningless. More of America (including unaffiliated voters in swing states) tune into the debates. The polling after the debates is much more meaningful in regards to how the general election will go. I will note that the polls are narrowing as we get closer to the election. As noted by 538 and other professional poll watchers -- it would be foolish to count Trump out despite his rather poor record over the recent four years.
Steve Martin, Eddie Murphy, Chris Tucker, Richard Pryor, I watch these guys when I want to be entertained. I certainly wouldn't think they'd make a great POTUS, regardless of how funny they are/were. The bar in 2020: Who will be the funniest in the debate. An old wise man once told me many years ago, "The same exact things that'll make you laugh, will also make you cry."
GOPers who were something a few years or more ago....I am not sure an undecided GOP is going to be swayed by Colin Powell still....I like John Kasich but he lost his relevancy already.