Warren and Biden are both on the way out.

Buttigeig and Klobuchar are gaining votes from those who have dropped support for the above two.
I think in the end it will be Sanders and Bloomberg. And maybe Sanders, Bloomberg and Klobuchar in the last three. But in the end Bloomberg, because he's the only sane halfway moderate choice who can attract moderate Democrats and compete with Trump in the general election.

To review, ALL the Democrat candidates for months have openly supported:

* de-criminalizing and/or amnesty for illegals.
* Government-funded HEALTHCARE for illegals
* Sanctuary cities
* the Green New Deal (with at least a 60 trillion-dollar pricetag)
* nationalized healthcare (with at least a 30 trillion pricetag), and in doing so ending private healthcare for 180 million privately insured Americans.


And I don't recall where each stands on these issues, but most or all support:

* de-criminalizing drugs, which would double or triple the number of drug addicts and cause federal, state and local government have to pick up the tab and pay for the damage caused. To say nothing of the thousands of innocent citizens who will suffer murder, beatings, drunk driving injuries, theft from these addicts, and suffer disease from these addicts.
* Allowing illegals to vote, either overtly or from deliberately unenforced laws that allow illegals to vote.
* Stacking the Supreme Court with liberal judges to make conservatives a minority.
* Eliminating the electoral college that our founders put in place to prevent just a few population centers from smothering representation for the rest of the country.
* Allowing criminals to vote in jail! (seriously!)

I've heard Buttigeig express support for de-criminalizing drugs, eliminating the electoral college, and stacking the supreme court within the last 2 days.

And I suspect that even the 2020 candidates who don't openly support these things would passively allow them to be implemented, if elected president.

Just like Obama didn't openly support them, but paved the way for them with an Obamacare that was calculated to fail and collapse, paving the way for a President Hillary Clinton to bail it out and replace it with nationalized healthcare.
And like Obama gave amnesty to children of illegals to deliberately create a growing tidal wave of illegals, that only Trump has been able to stop, and I doubt any other Republican or Democrat as president would have the resolve to do so.
And similar deceitful incremental erosions by Obama to undermine religious freedom, gun ownership rights, and forcing Christians and others to endorse and participate in things like gay marriage and abortion/birth control against their will.