These numbers portend to a massive swing towards Biden in the suburbs. It means we're likely seeing this play out in the suburbs of Des Moines, Milwaukee, Detroit, Grand Rapids, Cincinnati, Columbus, Cleveland, Pittsburgh, and Philadelphia. (Oh, and Indianapolis too, but that's not in a competitive state).
Grok what you are saying...
In many similar suburban places 2018 was likely just the opening volley of Cannon Balls at Fort Sumter South Carolina way back at the onset of the Civil War.
2020 now features suburbs in full Rebellion from Coast to Coast, against what has been an abject failure of Leadership on the part of the current POTUS.
Even similar places which did not swing Heavy DEM PRES in '16, are now making up for lost time, pulling out their brooms, and getting ready to drain the swamp of all of the corrupt Republican leaders, sycophants, fellow travelers up and down the ballot.
Sure, there might be some friendly-fire along the way, simply because Politicians in certain districts might have an (R) after their name vs a (D) after their name will accidentally become collateral damage as the Republican Civil War heats up, and they happened to pick the wrong avatar at a certain time in history where there might have only been one party contesting certain districts.