The Democratic Party has been many things over they years, many of them I do not identify with. You may recall that before Nixon's "Southern Strategy" of converting the solid Democratic South to the Republican side by using raciscism and racist reaction to the Civil Rights Movement as the bait to draw them over. It worked and along with Lyndon Johnson's support of Civil Rights set the dividing line.
And that gives us the base of each Party, that much remains today. Now of course there are strong influences within each party, neither of them is solely about race, but most of those came recently and are now the strong arms of each Party. The Republicans have been co-opted by, first, the Religious Right, and more lately the super rich. The Democrats are still giving lip-service to the Unions, but they don't actually support them. In fact modern day Democrats don't support much of anything. They don't enjoy the rain of shower from the Super Rich as the Republicans do, but they do just fine by the very very rich, just about one notch down from the Super Rich. Its the law and medical professions that donate to the Democrats and of course all of the same industries that pollute our political system on both sides of the isle.
If there was ever a country that needed a third party, a fourth party, and a fifth and sixth party too for that matter, this is the one. Or we could get away with just two if just one law was passed, one that would fix most of the political problems we have in this country. That law would provide public funding for political campaigns to the exclusion of private funding.