The civil war ripping through the Republican Party is familiar by now. But a similar battle inside the Democratic Party is just starting to emerge. Orthodox liberals are trying to mimic the tea party and impose political correctness on moderates.They point to the election of two left-wing heroes in deep blue states -- Sen. Elizabeth Warren of Massachusetts last year, and Mayor-elect Bill de Blasio in New York last month -- as a sign the party, and the country, is heading their way."In our minds, Elizabeth Warren is the north star to which the entire Democratic Party can look as they seek direction," Adam Green of the Progressive Change Campaign Committee told Politico.If the Democratic Party is foolish enough to listen to such nonsense, they deserve the defeats that will inevitably ensue.The Republicans provide a stark warning of what happens when an extreme faction dominates a mainstream party.