Bush lost because the economy wasn't healthy, Ford lost because (a) he was never elected President, and (b) he pardoned Richard Nixon's Watergate coverup. Trump enjoys an excellent economy, and nobody has been able to hang anything truly scandalous on him.
Presidents seeking re-election usually win. Over the last century, only four have lost. Additionally, they usually win by bigger margins — only Obama’s fell. On average, elected presidents who sought re-election increased their popular vote share by 2.1 percent. This last point is important: Incumbents do not just win — they get stronger.I could definitely handle Trump getting stronger in 2020. Schadenfraude is wicked fun, I’m imagining progressive heads exploding.