This article is an extension of the one I published August 4th in regards to the straw man attacks on the DCCC. I won't go into those details here but the issue outlined in the article is an example of the problem. A run to the far left will do nothing outside of relegating the Democratic party to a permanent minority. The Democratic party is currently in the minority across the board. The answer is to expand the base, not shrink it. This is especially important considering where the playing field is for the 2018 Senate. The chart below is a visual of safe vs not safe Senate seats.
Democrats are going to need to win over a a lot of independents and Republicans to win the races in Missouri, Indiana, Arizona, West Virginia, Montana and North Dakota. Ohio, Florida, Wisconsin & Nevada are more along the lines of states that Democrats should be able to hold so long as Trump stays at or below the upper 30's nationally.
If the Democratic Party is able to avert the Tea Party pitfalls and pull a rabbit out of the hat with a 50-50 minority: the map going into the 2020 election will be difficult. Democrats are fairly close to maxing out good pickup opportunities. They have chances in 2020 in Colorado and North Carolina. Maybe Iowa if things go well, and maybe Maine if Collins retires or decided to run for Governor in 2018. Democrats could possibly get Bullock to run for Senate in 2020 if he doesn't run for President. Maybe Democrats could coax Jason Carter into challenging Perdue in 2020 in Georgia. That is it.