Bernie Sanders is the most important 2020 candidate

Washington (CNN)On Tuesday morning, Jeff Weaver, who managed Bernie Sanders' 2016 presidential campaign, said this to C-SPAN's John McArdle about the possibility of a rerun by the Vermont socialist in 2020:

"He is considering another run for the presidency and when the time comes I think we'll have an answer for that. But right now he's still considering it."
That's both a) not terribly surprising and b) extremely important.
Not surprising in that Sanders has never really stopped running a national campaign since his primary loss to Hillary Clinton in 2016. Extremely important in that Sanders is -- and is likely to remain -- the prime mover in the Democratic presidential field.
    That's not to say Sanders is the current frontrunner for the nomination. He's not. Former Vice President Joe Biden is -- as CNN's Harry Enten argues convincingly here. 
    What Sanders' status as the prime mover in the race means is that he will set the terms on which the race is likely to be fought. He will set the margins -- in terms of policy -- for what Democrats are willing to say and do. He will be the person who the race revolves around -- either in agreement with or reaction to.
    It's already been happening. Earlier this month in a speech at the Brookings Institute, Biden used Sanders as a foil -- promising an alternate vision for both the problem and the solution to what ails the country. Here's the key bit from Biden: "I love Bernie, but I'm not Bernie Sanders. I don't think 500 billionaires are the reason we're in trouble. The folks at the top aren't bad guys. But this gap is yawning, and it's having the effect of pulling us apart. You see the politics of it."
    And, following the 2016 election, a parade of would-be 2020 aspirants -- Cory Booker, Elizabeth Warren, Kamala Harris, Kirsten Gillibrand --  signed onto Sanders' "Medicare For All" single-payer health care proposal. It's a role he played in 2016, albeit a somewhat unlikely one. Clinton, once she realized that Sanders posed a real threat to her chances, moved hard left on virtually every issue -- ensuring there was no space between her and the Vermont senator.
    The Point: Watch where Sanders chooses to make moves -- on both policy and politics -- in the coming months. And, as importantly, who follows and who chooses not to.
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