evidence: Presidential elections are decided at the margins, meaning how a handful of states shift from one election to the next can be enough to cast one party out of the White House and bring the other one in. This was certainly true in 2020, as Joe Biden edged out President Trump thanks to narrow victories in key swing states such as Arizona, Georgia, Michigan, Pennsylvania and Wisconsin — all states Trump carried in 2016. However, it wasn’t a uniform swing. The size and scope of these shifts varied, and many may not be lasting. Some formerly blue states returned to their pre-2016 status; some once-red states lurched to the left, in some cases even voting Democratic for the first time in decades; and some competitive states didn’t shift much at all. Below, we’ve broken out how 16 battleground states voted since 2000 and what the ever-changing Electoral College map could mean going forward. [...] And even though these states ended up in Biden’s column, his margin of victory was pretty narrow. He won Michigan by about 3 percentage points, Pennsylvania by a little more than 1 point, and Wisconsin by less than 1 point. Granted, Trump carried each of these states by less than 1 point in 2016, but Biden’s margins were slim and it's unclear moving forward whether these states will remain blue.