When AOC, arguably the most famous member of the House of Representatives after Pelosi herself, endorsed Bernie Sanders over Elizabeth Warren early in the Dem primary, it was a tremendous win for the Sanders campaign and the beginning of the end for the Warren campaign. Bernie managed to at one point climb to the top of the polls following AOC's endorsement and subsequent early wins, but then Biden's comeback in SC and on Super Tuesday put Bernie in the rearview mirror ever since.
However, theres an interesting little detail lost in the noise of all of this that few people realized: After a while, AOC stopped campaigning for Bernie
https://www.washingtontimes.com/news/2020/mar/13/alexandria-ocasio-cortez-refused-multiple-requests/
From Feb 11 to March 8th, AOC declined multiple requests from the Sanders campaign to have her campaign for him, to the point that getting her to rally for him in NH was the equivalent of 'Pulling Teeth' apparently. Following New Hampshire, AOC basically fell off the map for Sanders and left him on his own, and there are two prevailing theories why
#1) The plan was always a temporary endorsement before AOC had to go back to campaigning for her own seat in the House
#2) AOC was miffed at things Sanders did and treated her, namely accept an endorsement from Joe Rogan
Whichever the case/excuse may be, it highlights a fundamental problem that ultimately brought down Bernies campaign
If the case is the first theory, that AOC would only temporarily stump for Bernie before going back to her own business, then it highlights the lack of turnout and commitment by the progressive left..... A single seat in the House of Representatives, which will almost certainly stay blue in 2020, is nothing (to progressives) compared to the prospect of Bernie Sanders becoming the nominee of the Dem Party to go against Trump. Dems have never had a nominee like Bernie, and this was possibly their best chance to get it since Bernie was the frontrunner at one point. But then AOC disengaged....
When AOC, the literal posterchild for the next generation of liberal progressives, cant even stick with Bernies campaign past New Hampshire, then how on Earth could it be expected that anyone else would? AOC at one point worked for Bernie's campaign before she was even into politics herself, they endorsed almost every issue they had in common with each other, and STILL after a while AOC thought a better use of her time would be to focus on her own issues rather then keep stumping for Bernie..... When your biggest supporter (in terms of political clout) pulls out after just two contests, then your campaign and your appeal as a candidate is fundamentally flawed and restricted to a size that can never be big enough to capture the nomination.
If the case is the second theory, that AOC started to disengage chiefly because Bernie, among other things, openly welcomed an endorsement by Joe Rogan, then it just brings the 'purity' weakness back into question, the idea that Bernie never set out to expand his base from what it was in 2016, and would be openly hostile towards those who were not completely in line with the entirety of his platform..... We saw this towards the end of the primary this year in 2020 when Sanders and Warren supporters became openly hostile with each other over minor details, and even Warren's shift from Medicare for All to a transition plan cost her about half her support over time even though her ultimate goal was to still aim for Medicare for All.
Do you think Joe Biden's supporters give much of a shit about how in tune all of his supporters are with his overall policy positions? Fuck no, they like him mainly because they think hes the best bet to beat Trump and that he was Obama's VP for 8 years..... When Buttigieg, Klobuchar, and Bloomberg all pulled out of the race, their support almost unilaterally joined up with Biden's base for those exact reasons. Elizabeth Warren dropped out most recently, and there isnt much of a sign that her base went even in a majority with Sanders. (Warren polled at almost 14% nationally before pulling out, Bernie's numbers since then have only increased 6 points from 29% to about 35% https://www.realclearpolitics.com/epolls/2020/president/us/2020_democratic_presidential_nomination-6730.html)
If AOC decommitted to focus on her own campaign, it shows that the progressive left are simply not as enthusiastic about Sanders as some of his online supporters loudly claim to be. This is also backed by lack of turnout with the youth vote that Sanders was banking on.
if AOC decommitted as an objection over Sander's embrace of Joe Rogan, it shows that the desire for purity and uniformity among supporters is more important to the progressive left then the overall number of them, where they would prefer to be at 30% and all on the same page then at 60% and pretty diverse. This can be backed by the hostility between Warren and Sanders campaigns despite the two being the closest together in terms of ideology.