The main reason that Trump is still generally favoured to win the election is that the US economy is doing well. Nor has there been any crisis that has affected undecided voters in ways that could change their perceptions of his Presidency. A corona-virus epidemic is the most likely risk that could test those propositions between now and November. Could this be Trump's Hurricane Katrina - the event that finally exposes the implications of his Administration's incompetence?
https://www.vox.com/2020/2/25/211505...virus-cdc-cuts
https://www.politico.com/news/2020/0...request-117329
One thing that seems likely is that the Administration will continue to downplay the risks. This is exactly the sort of situation in which people need to be able to trust what officials tell them, yet Trump and his acolytes have completely trashed that credibility.