True nationally, and I expect the same from Joe Biden. I expect Joe Biden to win the popular vote by a far greater margin than Hillary did.
I have no science to back this up, but in swing states I think (fear ?) that there's a significant gap between what people say they're going to do and what they actually do.
Speaking from personal experience, it's very difficult to be a lifelong supporter (and in my case member and party activist) of one party and then to actually cast your vote for another party in an election. On two occasions I went into the polling booth fully intending to cast my vote for another party but ended up voting for the party I always voted for.
We seem to have a number of lifelong Republicans who say they're going to vote for Joe Biden. It's going to tough for them to actually do that - however well intentioned they are.
......and all of that excludes any post-election shenanigans which IMO no polling organisation or analyst can take into account because we have no idea how effective they may be.