The reason is simple: incumbency has its privileges. Since 1900, 20 presidents have run for reelection. The incumbents have won 15 times and lost five, if you include former President Gerald Ford who was never elected at the ballot box in the first place. If you remove Ford from the equation, the winning percentage among presidential incumbents would likely be good enough to capture baseball’s Cy Young award in recent years.
Further, despite the chirping of the pundits about what 2018 means for 2020, recent history has shown that there is in fact very little correlation between a president’s first midterm election and their reelection bid. Case-in-point, Bill Clinton’s party lost 52 House seats in 1994 and Barack Obama’s party lost 63 House seats in 2010, yet both men garnered more than 330 Electoral Votes in 1996 and 2012, respectively.
Add in the fact that the 2020 Electoral College playing field will likely be very similar to the 2016 edition (40 states are essentially already decided and 10 are up for grabs), and one starts to see why Trump has a very real chance of securing four more years in the White House. To prevail, the Democratic nominee would have to either sweep the Rust Belt (Pa., Wis., Mich., Minn.) or dislodge Florida or Arizona from Trump. Not an easy task.