I have a friend who contracts with the DNC and has access to more accurate internal polling. They're not the sort to sugar coat and shill for bad people on their side either, they've shared a lot of information about really nasty corruption and horrible behavior in their ranks (some from people you would expect, some from people you wouldn't). Their data has proven to be tremendously more accurate than any of the publicly shared stuff. They accurately predicted results since 2016, both with the presidency and the senate/house. This includes the midterms where they were spot on about the senate/house results. And they also knew Hillary Clinton was going to lose the electoral college in 2016.
For what it's worth, my friend isn't worried about Biden's chances at all in 2024. This sort of confirmed my own suspicions, and i'm not even a fan of Biden myself (though he's been more tolerable than I expected despite congressional gridlock). Biden is expected to win in 2024 and also potentially do better than he did in 2020. He's actually won over a lot of progressives who were skeptical of him at first. And his pro-union stances have also endeared him with both lefties as well as a wide variety of blue collar workers. He'll also have an incumbency advantage now. Granted, we're still a year away and anything can shift the tides.
The midterms are also pointing towards Democrats being much stronger than media/polls claim. It wasn't anywhere near the sort of red wave blowout everyone was predicting. Midterms are usually a bloodbath for unpopular presidents, but the Republican gains were quite lackluster. They won the house by a slim margin (most of which wasn't even because of popularity of their candidates over Dems, but rather gerrymandering), but lost a couple of seats in the senate so that Dems upped their majority a bit there. Democrats have also been doing extremely well in a bunch of local and special elections lately. With abortion stances in particular having devastating effects on the Republican party, far moreso than I personally expected (but again was predicted by my source).
It should be noted that public polls are manipulated by shoddy questions and cherry picked demographics. This isn't new either, a ton of polls were dead wrong about both 2016 and 2020 elections. But there's also outright intentional dishonesty from the media as well. Corporate media actually love Trump because he was a ratings factory for them. But ever since Biden was elected, there's been a massive dip in ratings. And that isn't acceptable to investors or executives who demand constant ever increasing unsustainable growth into infinity. He's actually very sorely missed by the executives running all of these conglomerates. They want him to win in 2024. Regardless of what they pretend otherwise or whether they're perceived as conservative or liberal leaning.