Try reading Pew Research findings and Gallup Poll. In the last 10 years, the biggest gain has been those who select "non-affiliated/independent". It's up 9% since 2004 per a 5/2015 Pew Research Study. Gallup's numbers are more instructive: In 2/11-14/08 40% respondents identified as Democrat; 34% Independent; and 26% GOP.  In 75-9/17 Gallup respondents were: 28% Democrat; 45% Independent; and 25% GOP. http://www.gallup.com/poll/15370/Party-Affiliation.aspx.

Reasonable minds can disagree with numbers based on"snapshots" in time, what does "leaning" affiliation mean, etc.? Based on both well-respected entities research, Independents are making substantial gains at the expense of the Democratic Party. That would make sense based on the popularity of The Bern's "Utopian Free World" vacuous promises. The Demos face a yawning chasm of credibility. Full-bore socialism ala NYC De Blasio, Corey Booker, Sanders, et al, or Democracy?