What the heck world are you living in?
It's pretty clear that we need to go back to the Democratic party of FDR rather than the corporatist party we've had after Al From's 1992 bloodless coup that put Clinton in the White House when we got in bed with the big banksters.
Rather than corporatists and moderates we need more progressives like Bernie Sanders and Elizabeth Warren. That's the only way you're going to energize the base.
The democratic party is failing because it forgot who it is and sold its heart for money. I seem to recall reading somewhere about some right wing big donors of the democratic party that are actually republicans that want to move the party in such a way that it fails and ensures republican control. When you make the democratic party about doing what's best for big companies then the party of the people loses its meaning. The energy and support disappears, and the party loses.
Though, depending on how badly Republicans botch the next 4 years we might not need to do a damn thing to take over.
As for Republicans... They need to get away from hate, being completely sold out to big corporations (oil, military, pharma, etc), and religion. If they did that they might even flip a lot of democrats over to the republican side. There are a lot of people that believe in more conservative governance but the way republicans throw the poor under the bus and prop up huge corporations at every opportunity and how bat shit insane they are on issues like gay rights, trans rights, abortion, etc, just scares people away. Hell, if they actually did that I wouldn't be so damned ashamed of half the country being Republican. As it stands they want to get rid of public education (the fuck?!), medicare, any kind of social welfare program, and scaremonger people against universal healthcare so they can line their pockets from big pharma. It's all about money. They need to get away from that shit.
Overall, we need to get all money out of politics. That would solve a lot of fucking issues on both sides.
edit: Oh look, an article: https://progressivespring.com/2017/02/01/justice-democrats-democratic-party/