There's nothing like the love and respect that the far-left candidate who wins the Democrat primary shows for the centrist candidate who loses.

And there's nothing like the enthusiasm this results in on behalf of the supporters of the losing centrist.

N.B., three items.
(1) No leftist Dem who defeated the centrist has won the general election since Andrew Jackson in 1828 (Yes, Jackson was the "left" candidate in '32).
(2) No Dem since Cleveland/Stevenson (1892) has been elected president without a Southerner on the ticket (Stevenson was from Kentucky, Cleveland from New York). The last winning Dem ticket without even a border-state Democrat on the ticket was Cleveland/Hendricks (1884). Hendricks was the governor of Indiana.
(3) No Democrat has ever been elected without carrying at least four states of the old Confederacy. (Clinton, 1992, 1996) (Lewis Cass lost election in 1848 despite winning four, Andrew Jackson lost in 1924 despite sweeping the South, excluding Georgia. Texas, Florida and Arkansas were not yet states.)