Imagine a legislative district that which was 100% comprised of Democratic voters -- and more specifically, partisan Democratic voters who are guaranteed to vote Democratic in the general election. There is no chance any of them would ever vote for a Republican -- they are committed Democratic partisans. In an open seat primary race, what intra-Democratic ideological position on a scale from left to center (i.e., from AOC to Kyrsten Sinema) would be most likely to win?
One might think that this is exactly the sort of district an AOC-type is most likely to win. Voters who are committed Democratic partisans would prefer the left-most candidate who is still within the broader spectrum of Democratic positions. The more firmly Democratic you are on the axis of partisanship, the more firmly progressive you are on the axis of ideology. Put differently, Democratic partisanship can be recast as "unwillingness to vote GOP". The further away you are from the GOP ideologically, the less likely you are to vote for them; so if we encounter a population that would never contemplate voting GOP, it stands to reason that the explanation why is that they are ideologically most distant from the GOP -- i.e., the most progressive voters. It's possible that such Democrats might vote strategically in races where electability is a concern -- choosing a more moderate option than they'd prefer in order to ensure they prevail in the general. But where electability is no barrier (as in our hypothetical 100% Democratic partisan district), their ideal-world preference would be the candidate representing the Democratic Party's left flank.
But there is actually a lot of evidence that this isn't necessarily true. Consider Chryl Laird and Ismail White's book Steadfast Democrats, seeking to explain why the African-American community so overwhelmingly affiliates with the Democratic Party -- circa 90% support for Democratic candidates in national elections. One answer would be "because they have overwhelmingly progressive political views". But, while it is likely the case that the Black American community nets out towards being more progressive than the White American community, there still are plenty of moderate and conservative African-American voters -- many if not most of whom also consistently vote Democratic. They are steadfast Democrats for reasons that don't map on perfectly to ideology.
For these voters, partisanship does not necessarily translate into preferring the most progressive available option even in a Democratic primary (so one is choosing among Democrats) where the winner is effectively guaranteed to win the general (so one's choice isn't an electability trade-off). Such voters are both consistent Democrats and might prefer a Joe Biden sort to a Bernie Sanders or Elizabeth Warren sort (or a Shontel Brown sort to a Nina Turner sort) on the basis of ideological preference. And (as committed partisans), such voters are especially likely to recoil from campaigns that appear to be antagonistic to the Democratic Party -- there's a reason why this was far and away the most powerful vector of attack for Brown against Turner, or Biden against Sanders for that matter.
To take a striking example: while Black voters in general are more likely to identify as "liberal" than White voters, Black Democrats are considerably less likely to identify as "liberal" than White Democrats are. 55% of White Democrats describe themselves as liberal, compared to just 29% of Black Democrats (almost identical to the 25% of Black Democrats who characterized themselves as conservative). How can this be? One way of thinking about it as follows: If you're a White liberal, you're almost certainly a Democrat, if you're a White conservative you're almost certainly a Republican, and if you're a White moderate you could be either (or a swing voter). By contrast, if you're a Black liberal, you're almost certainly a Democrat, if you're a Black moderate, you're still almost certainly a Democrat, and if you're a Black conservative, it's still pretty darn likely you're a Democrat. So if you're trying to appeal to the "steadfast Democratic" constituency of African-American voters, that means appealing to a cadre that is probably quite diverse in ideological orientation -- including liberals, moderates, and conservatives.
I think this analysis also tracks onto Jewish votes, though I'm less familiar with scholarship on the topic. Jews are famously also one of the most steadfast Democratic demographics behind African-Americans, regularly voting Democrat at rates around ~70%. And, while on net Jews again are certainly more liberal than the average American, Jewish Democrats don't necessarily cluster onto the left-edge of the Democratic Party. For Jews, too, the fact that we're an overwhelmingly Democratic voting bloc does not necessarily mean that the best way to appeal to us as a candidate is to be as progressive as possible within the broad spectrum of Democratic Party opinion -- even in circumstances where "electability" is a non-issue.
It is notable to me how groups which seek to crack Jewish communal attachment to the Democratic Party often sound very similar in rhetoric to "Blexit" type organizations on the right. They'll typically speak of how they were "raised Democrat", how it was part of their "mother's milk", how for a long time it was "unthinkable" to even contemplate voting Republican -- all lines which speak to a connection between Jews and Democrats which is as much cultural as ideological. To be sure, such appeals will only have limited success given that there are only so many Jewish conservatives and because the "cultural" reasons which bind Jews and Democrats together remain quite solid. But it is notable nonetheless.
Why does this matter? Well, it suggests that the Democratic Party's base -- defined as its most loyal, committed supporters (of whom both African-American and Jewish voters certainly qualify) -- is more ideologically heterodox than one might think at first glance. They're certainly considerably more liberal than the country writ large, but it's not necessarily the case that they're thirsting for the most progressive possible option only to be thwarted by a party apparatus that takes them for granted. It's entirely possible, and I'd say likely, that their preferred Democrats are liberal Democrats who still maintain some distance from edge of the Democratic Party spectrum -- so not a Kyrsten Sinema, but not an AOC either. More like a nice, comfortable Chris Van Hollen.