The launch of the Dem campaign starts with their two debates in a few days. Expect a fight. Expect the unexpected...Expect Biden to lose (prediction) and somebody else to steal the momentum and be a genuine challenge.
Expect lots of shenanigans regarding ballot harvesting, fake votes, etc...
And never underestimate the depths the media is willing to sink.
Expect Chinese money to get in the way somehow...and play a role.
What people don't realize is that last time the polls all said that Hillary's chance for election was close to 100% and that President Trump's chances were close to 0%. The morning of the election, the New York Times had Hillary's chances at better than 85%. The left was utterly dismissive of President Trump.
The tendency of those who believe in this level of success is to get lazy. The Dem voter fraud machines weren't cranked up to 11. Dem people who were busy or had other things to do didn't make an effort to get to the polls: "they don't need my vote, this is a sure thing".
Although the polls already are such as to inspire overconfidence in the Dems, this time they are not going to take any chances. Turnout is going to be crucial particularly in those states where it was close before. Voter fraud will probably be the worst in the history of this Republic.