In 1864, during the height of the Civil War, both the Democratic and Republican parties held their nominating conventions as usual. The Democratic convention was held in Chicago and nominated what was, at that point, the youngest ticket ever—George McClellan (37) and George Pendelton (39). The Republicans (temporarily called the National Union Party) held their convention in Baltimore and re-nominated President Abraham Lincoln.
However, in 2020, the COVID-19 pandemic is likely to dramatically alter the nominating conventions of both parties—each scheduled for late August. Already, Democratic Party Chair Tom Perez has set the stage for what would essentially be a 'virtual' convention in Milwaukee. And, presumptive Democratic nominee Joe Biden has explicitly called for an all-online convention. President Trump, on the other hand, has been urging that his party's convention in Charlotte be a traditional one—nationally televised with throngs of cheering delegates, However, even some of North Carolina's Republican lawmakers are already casting doubt on that possibility. In all likelihood, there will be some type of scaled-back version that puts a high priority on delegate health and safety.
So, even during a deadly and divisive Civil War, America's presidential nominating process went ahead without interruption or serious alteration. And yet, 156 years later, a deadly and persistent virus is likely to fundamentally change how we choose our candidates for Commander-In-Chief.