Looks like Trump vs Biden, and. if this coronavirus thing doesn't blow over soon, it does not look good. The virus has already had enormous economic impact. It is a strange reaction, if you compare it to the number of infections and deaths caused by the flu virus every year.
I'm probably in the minority in thinking that Bernie Sanders has a better chance of defeating Donald Trump than Joe Biden. The reasons being:
1. Bernie Sanders has much more enthusiastic supporters than Biden. They remind me of the supporters of Barack Hussein Obama, Ron Paul, and Donald Trump in that they attend campaign rallies in large numbers and a high % will rip / attack those that criticize their candidate. On the other hand, most Biden supporters are mainly anti-Trump. That increases the chances of many staying home on election day. Much like with John McCain, Mitt Romney, and Hillary Clinton.
2. Sanders is much more capable in debates than Biden. The more Biden speaks, the better it is for his opponents. A gaffe seems inevitable with him.
As for the virus, I think the situation in October and early November is what's most important regarding the impact it will have on the November Elections.