Well, in fact it's the Democratic Party which became totally radical and polarized over the years. No one can survive a Dem Primary without either massive minority or socialist/socially liberal support. It is far more possible that a Moderate earns the GOP Nomination than the Dem Nomination.
Schweitzer would be a very dangerous opponent in 2020, thank god he won't be it.
Eh...Hillary Clinton just won the dem primary earlier this year. Before that Obama, Kerry, Gore and Clinton won. Whereas the GOP just nominated Donald Trump over a whole bench of "electable" republicans. So where is the evidence for this outlandish claim?