Democrats have a problem and it is the economy. According to this Pew Research study from May of this year, people did not feel great about the economy, and those feelings are strongly partisan. When Trump was president, Republicans thought the economy was great, when Biden was president, they thought it was terrible. A lot of this might have been driven by pandemic related lock downs, but regardless Republicans loved the economy under Trump but hated it under Biden.
Ok, so does that mean that Democrats thought the economy was terrible under Trump but great under Biden? No, not really. Democrats don't seem to be nearly as partisan in their opinions on the economy. 39% of Democrats rated the economy as good or excellent by the end of Trump's first term, and 37% rate it as good or excellent today. It seems that Republicans are much more about partisan vibes: things are great when our guy is in charge, terrible when their guy is in charge. Everyone else seems to be much more negative on the economy in general, regardless of which party is in power.
That is bad for the Democrats. America is divided, but we're not all divided in the same way. Republicans are remarkably unified. Everyone else is very fractured. There is no single block of non-Republican Americans that can rival and counter the Republican block. They are unified, the rest of us are not.