As I have written, Hillary Clinton's 2016 campaign began in around 2007 when she realized that Barack Hussein Obama was going to get the Democratic nod for 2008. For her cooperation aka "silence," she was promised clear sailing in 2016, which she got. She spent a good portion of that waiting time sewing up all of the heavy donors, so that nobody, with a chance, could afford to run against her.
There's already talk about Michelle Obama running for the Democrats in 2020. She does have a strong chance to beat some Republican contenders, unless the Right versus Left demographics, family size, continue to influence voting results. While the Left in America will gladly vote for a woman, regardless of her policies, the Right is more cautious and is wary of another Obama in office. This has nothing to do with gender and color. Many are terrified of the America being planned/envisioned by the Left and political Democrats. So even the most feminist of Republicans will prefer voting for a man who shares her ideology.
And in the Republican Party, those who are hoping for 2020 to be their year are already trying to make points around the country, like Ted Cruz. The Republicans had a nice healthy, young crowd who competed against Donald Trump during the primaries, so no doubt that a few of them will use that experience to try again for the Republican Nomination.
Let's just pull up a seat, since the show has already begun.