DNC has being making mistakes and individuals like Omar are causing controversy that makes them look bad. All while having the Mueller report fall back on them, a solid economy, and other factors that are forcing them at times to fall back on prior marketing/campaigning like the tax changes that already done and set. The Republicans had their own disarray and came close to the brink, but it was when the GOP leadership realized Trump had the chance to win, they stopped pushing against him and rallied behind him (don't forget, the GOP leadership was against Trump for a very long time during the primaries, they caved to his popularity and saved their party, though at a cost).
If the DNC wants to win they need to stop Omar from making Israel an issue, as they will lose on it especially when a lot of the DNC funding comes from Jewish donors. Also, they need to ensure they do not encourage purity tests, the whole "You aren't my friend if you don't agree with me" spiel (its always funny when the guy who can barely maintain a few friends has an ego trip and thinks this will work), and other stupid methods that disenfranchise large populations of voters and overlook the possibility of changing peoples minds. You need keep everyone in the same pool of Americans so that no voter is thinking that voting Dem is like voting for another country, it needs to feel like just another part of the USA. If the DNC's voter base keeps playing the us or them game, they will lose again.
Lastly, and most importantly, they need to just have Biden go up against Trump. No rigging the primary again, just get the other potentials to realize that Biden is the safest bet, especially compared to the others he is running against for the primary. They shouldn't play any games or try to pull some "Lets get an X in the white house!" else they are just giving away the election.
