Yes (at least the story from Friday afternoon says that Bernie is just days away from making the announcement).
How big a deal is this?
First, lets be honest....nationally, Bernie was barely known in 2016, and yet managed to almost out-run Hillary Clinton. In the Iowa caucus, Bernie won. If you round up a hundred working-class Democrats, at least half of them are fairly open to a Bernie theme.
Second, Bernie picked up a lot of lessons-learned in 2016.
Third, in a straight Bernie-Trump situation...I think he could easily take Michigan and Ohio (both states that Trump took in 2016). That's a 34-Electoral College-shift. It's enough to win.
Fourth, if you gaze across at the twenty-odd characters that the Democrats will front in 2020.....no one perks up crowds like Bernie does.
Fifth, while Bernie's wife is in a bit of a scandal.....no one really cares.
Yeah, I'm suggesting that this 2020 election would be tough for Trump to win. But adding to the fury.....if Trump decides NOT to run? Bernie could easily win against the typical list of GOP candidates.