A.B. Stoddard asks at Real Clear Politics which Democratic presidential candidate other than Joe Biden can appeal to middle-of-the-road voters.

As Biden creates doubts about his viability, there is no one else positioned to wrest support from the center of the electorate with a broad enough coalition to win in November 2020. Party elders can foresee a nightmare scenario in which Sen. Bernie Sanders fades, Warren consolidates enough support from his voters to topple Biden, then becomes the nominee and loses the general election.

Last weekend at the Iowa State Fair, when Biden made mistake after misstep and Trump proclaimed that he “isn’t playing with a full deck,” the contrast with Warren was painful. Her crowds were large and excited, his were not. …

… The whispers are mostly made off the record and on Twitter, not yet from major players in television or newspaper interviews, but the talk is the same: What if Biden is too outdated, fatigued and forgetful to make it another whole year to the nomination and then to next November, when he will be just shy of 78?

For now, Warren is the Little Engine That Can to Biden’s Big Engine That Perhaps Cannot. While the center of the electorate is reeling from our current turmoil and craves stability, Warren is promising “big structural change” and has eclipsed Bernie to become the beloved progressive in the race.