O’Malley, Chafree, Sanders, whoever - these are not household names. I bet most Americans have no clue who they are. The hill is too steep for them to climb.
I think it is better with more candidates, but here is the problem of a party having a President incumbent after 8 years - no one in the party has run a national platform for 8 years.
Hillary has overcome that with two advantages: 1) Bill, 2) being SoS under Obama.
No one else has.