Democrats "voted their hearts" in primaries for decades and lost election after election for President because their candidate was too left for the country. I know, the first time I could vote, I voted for George McGovern.
They finally broke that cycle when they voted for a moderate, centrist Dem in Bill Clinton, and their entire agenda profited.
And when, against all odds, they finally did get a (supposedly) more liberal candidate in Obama, they turned on him viciously when he governed is a less than far left way to accommodate the economic and national security realities we face. Stateless warfare did not cease to exist the d'day he was elected, much to the shock of some.
Which backstabbing is one reason, I think, that Liz Warren doesn't want to run. The real world tends to intrude on purely ideological efforts.
Far lefties constitute what percent of the voting public? Let's be very generous and say 15 percent. They couldn't get elected dog catcher without appealing to people who don't hold all their same policy beliefs, most of which some of we more pragmatic liberals share.
It' great to have Bernie in the race and if it ever looks like he might could win the general election, I could easily vote for him. But he's no charismatic orator like Obama, and it won't be easy for him to become the first "independent socialist" President.