Nothing is killing our democracy more than the unlimited amounts of cash that mega rich individuals and special interest groups can give to their chosen candidates IMHO.  
Back in the 1960s and 70s my state had Senator William Proxmire, who started the Golden Fleece Awards that exposed wasteful  government spending.  He took no money from big corporations or other special interests.  One year he won reelection by spending all of $480 out of his own pocket.  Hard to believe, I know.
These days he'd be steam rolled out of office by a few individuals with deep pockets.