There used to be room in the Democratic Party for conservatives. Much like the Repubs, who have purged all the liberals and nearly all of the moderates. Many would go back if the Dems tolerated dissent on issues like abortion, gay marriage and so forth. The economic issues aren't what turns off those voters and the polling has reflected for years that 2/3 or more of Americans support things like raising taxes on the wealthy, raising the minimum wage, placing higher tariffs on imports and so forth.
Dems don't speak their language. They completed ceded religion to the Repubs and they will pay for that. Bill gets it. Listen to Bill's speeches in the 90s and sometimes now, and you will hear language rife with religious tones. Consequently, you have someone who can carry Southern states. (Hillary will win a few she shouldn't just because her opponent is a complete moron.) Sooner or later, the Repubs will nominate someone from NY or California and the Dem nominee will be screwed. Then he/she will have to poach from states the Dems haven't won in years and years.