How do we know that Trump votes are going to show up on election day. Maybe Republicans are deciding to vote early just in case. Could we already be burning through votes at a similar rate as Democrats?
I’m going with the hat guy.
Yes, we could. If the Democrat advantage in VBM+IPEV in critical states like NC and FL is reduced to 0 or less by Tuesday, then it's hopefully not a problem. But even then we still don't know who those voters picked; we only know their party registration and in many places (MI, WI, TX, GA...) we don't even know that.
Hanging our hats on the assumption that we're going to slaughter the Democrats (figuratively, of course) on election day because that's what happened at some point in the past is directly at odds with the unusually high number of Republicans voting prior to E-day. "Cannibalizing" isn't just for Democrats anymore. In many places there will probably be more R than D left to vote on 11/3, but our side still has to actually show up because we're relying on a major advantage on that one day. After 11/3 we'll see big gains for the other team.