I think you need to support the person you believe in.
"Belief" won't get you a dime for a cup of coffee. You might think it does, of you don't regard the dismal folly of the Trump "presidency" as an existential threat in several dimensions, or if you really like your politics "WWWF"-style -- something no sane patriot 250 years past or hence would countenance. Well -- maybe Nathan Bedford Forrest or some such clown, but that's no sane patriot.
There is too much "belief" circulating within and without our politics. God is not part of the Constitution; it is a contract between "We the People" to form a "More perfect Union". God was only invoked in the Declaration of Independence because such was the tradition and habit of authors or statemen of the time who dealt with Sovereigns who might cling to the Divine Right of Kings. Hobbes did it; Locke did it. The authors of the Declaration did it.
Property is not "God-given" -- the rights are assigned by the State and the Law.
So Libertarianism, White Supremacism, Laissez-Faire Capitalism, "So-shal-ism" are all ideologies, and people put their faith in ideologies -- lazy crutches for True Believers.
You can believe in people if they have a track-record for public service. Trump doesn't have a track-record of public service. Even his track-record for charitable activities is a fraud. Trump doesn't believe in anything, but his followers -- True Believers -- either believe in Trump, or hate everyone else.
You can "know" that you have different "toolboxes" to solve problems -- that's near-certain and not whimsical "belief".
If you want to belief in something regarding the day-to-day and long-term policies of self-governance, believe in three things:
-- Common Sense
-- The Constitution of the United States of America
-- The general Principle, namely -- The Rule of Law
The "Socialist" label makes Sanders vulnerable to the Fascist Incumbent, much practised in spinning the Big Lie. And Sanders, who carries the day with expounding Moral Issues of our time, is too inflexible in his old age. His inflexibility is woven together with Belief. For that, Biden has his better moments, and at least has a childhood disability to excuse for his occasional gaffes and confusion.
Win the White House. Win the Senate. Put the Wrongdoers behind bars. Forge a policy plan that folds Sanders, Biden and the rest into a solid proposal.
And hopefully, we shall all live another year to see it happen.
So -- Yes to #1. Changing at the last moment really isn't an option: The People -- chose Biden even if I voted for Bloomberg. I voted for Bloomberg, but I would be happy with many of Sanders' policy proposals.
As for #2 and the "rest of them", I suspect that some of them had a better chance than Sanders, and some of them bring the question to its brink, with marginal poll results over Trump. Warren may have been one of those. But -- I would be happy with many of her proposals!
Apparently, the Inner Circle of Demon-worshipping Trumpers believe Biden has the best chance to win, or they wouldn't have wasted resources and credibility on the "Ukrainian back-channel", and Trump wouldn't have risked prosecution during or after an impeachment or an electoral defeat.
We commend ourselves to the Almighty! Let slip the dogs of campaign war!