If you want a third party that represents the more moderate components of both parties you will have to build it from the bottom up. Until you get those folks into city, county, and state governments it won't fly nationally. Elect better Congress critters. A strong congress can better control an idiot president from either side. Make the extremes unelectable.

Which is why, consistently, WA does not elect a GOP Governor. To get nominated, the candidate has to cater to the extreme right. The Dems just have to avoid looking really stupid. Really, really stupid.