Two points… it is not “blatantly unconstitutional for the Democratic party to refuse anyone the right to debate on their stage. Lately, Democrats cry “constitutional crisis” and “unconstitutional” at things they don’t like. Not liking something does not make it a constitutional crisis… a personal crisis maybe… The constitution does not express any opinion on how parties would run themselves… it does not even acknowledge parties existed.
Second point, that said, while the Democratic party makes its own rules to a large extent, I think the party effectively “sacrificed” Biden this week in an attempt to impeach Trump. Whether one agrees or disagrees over whether Trump did something wrong, there is no question that the “facts” about Biden’s behavior raise serious issues among honest Americans over whether he is fit to be President.
Let the lawyers figure out the laws, but imagine what the media would say if Trump’s children were selected to sit on various Boards earning millions of dollars and Trump just happened to pick those companies products as exempt from tariffs. No proof, just the appearance of a conflict of interest would set the country abuzz and Dems crying for impeachment, why do they think people give Democrats a “free” pass, they don’t.
Biden already had his issues, this last one is likely the final straw. Which means his present support at some point in the future is going to shift to other candidates. Traditional wealthy liberals are going to shun those candidates like Warren and Sanders promising to break up their companies and bury them with complex wealth taxes that no one will be able to understand.
Somewhere a “compromise” candidate is going to rise up, who embraces enough progressive ideology to keep those progressive liberals on board and yet is less threatening to southern and Midwestern Democrats and independents who reject much of progressive ideology, but are willing to accept a little to regain the White House.
Most of the current Democratic hopefuls have thrown themselves so far left that when the times comes for them to convince the rest of the country they were just kidding in order to capture votes from the middle, they will come across as pure hypocrites. Some of the less followed and less supported candidates that have not done so may in fact have the best chance of winning a general election.