I’ve seen more than one post from people complaining that AOC was supporting Bernie instead of Biden because she was one of the people nominating him at the Democratic convention last night.
That’s not true.
Bernie delegates are required by the rules to vote for him on the first ballot. If Biden did not get a majority, then they could switch their votes on the second ballot.
And under the rules, someone has to officially nominate him and someone has to second the nomination. Someone has to do it.
So someone did, and she seconded it. It was a formality. She had already long ago endorsed Biden. She spent most of her sixty seconds talking about issues that were important to her and then, at the very end, seconded the nomination because it had to be done.
Now we can discuss whether politically she should have done this (as opposed to letting someone else take on that job), but that is a separate issue.