Is it 2020 yet? No, but the process is already underway
But who? Elizabeth Warren and Bernie Sanders are already positioning themselves to represent the Crazy Left. Sen. Al Franken of Minnesota is thought by some to be considering offering himself as a different kind of national joke next time around, representing, in the terms of the classic Monty Python sketch about a parliamentary election, the "Slightly Crazy Left." Martin O'Malley is said to want another shot at representing the conventionally crazy Democrats, as are freshman senators Corey Booker of New Jersey and Kamala Harris of California. Joe Biden is making all the moves of a candidate while insisting that he is not one. Fanciful possible candidacies (almost as fanciful as Donald Trump's was, by people equally unqualified to be president) include those of Oprah Winfrey, Michelle Obama, Mark Zuckerberg, and Mark Cuban.
There's even talk that Ohio Gov. John Kasich may challenge President Trump for the Republican nomination. I wouldn't be surprised to see Sen. Ted Cruz of Texas mount a challenge. I can't see either of them winning, and I'm still looking for an option outside the two major parties- another try by Evan McMullin, perhaps, after being elected to the Senate as an independent from Utah, or by some other centrist out to confront the divisiveness and extremism of the political status quo.
In any case, here's an article at FiveThirtyEight.com on the (very) early signs for 2020. I myself, being a political junkie, relish the process. And being on most days a reasonably rational human being and an American patriot, I can hardly wait for Donald Trump to be over.