The problem for democrats is that if they don't like the democratic candidate they wont vote for him/her. Republicans will vote for whoever is trotted out there, doesn't matter how big of a steaming turd that person is, as long as there is an (R) next to the candidates name, that's good enough for them. See Trump as an example of that.
Evidence, please. Remember all the LW jokes about "the Republican clown car"? The Democrats were given two choices; Bernie and Hillary. Thanks to the *******, godless Russians, we know Hillary was a shoe-in and Bernie never had a ******* chance due to the DNC. OTOH, the RNC was pushing Jeb!, but they weren't corrupt like the DNC and he soon fell out.