Maybe the strongest part of the case that Trump now needs an “Act of God” to beat Biden is that almost all of his possible escape hatches have been already closed off.
At the start of the coronavirus crisis, I theorized that liberal forces were going to cause football to not be played this year and that this might help Trump politically. While liberals have indeed laid the groundwork for that to eventually happen, they are not going to get widespread public blame because the waters will be too muddied, and the virus is not nearly under control enough for Trump to credibly claim that killing football is a gross overreaction (if anything, I now see this working against Trump as it will depress part of his base).
Similarly, I thought that turning the election into a referendum on mandatory mask-wearing was going to be a potential winning issue for Trump. However, partly due to the virus being seen as still out of control, and a shockingly high percentage of formerly freedom-loving Americans being in favor of government having the authority to mandate this, it has worked out in the opposite way, and Trump has effectively waved the white flag on the topic.