Hardcore progressives have promoted a national police force at least as far back as the 1930's as expressed by one of FDR's brain trust, Rexford Tugwell. Of course, as with most of the more "extreme" wishes of progressives, especially unconstitutional ones, not much was, nor is, publicly made of it. The Constitution delegates police power to the states, not the federal government. So our "analysts" of politics in the media or in academe either don't think it would ever happen, or they secretly hope it does.
In the meantime, federal intrusion into local policing has slowly but gradually grown. Either by direct implementation such as providing funds for hiring more police, or equipping police departments with various weapons or equipment. Of course, with federal "aid" comes attached federal strings. If not explicit, federal wishes are implied or recommended by "guidelines" or by changing guidelines for federal officers which are hoped and implied to be implemented by state and local police departments.
Eric Holder has created another one eliminating racial or ethnic or group profiling:
http://news.investors.com/ibd-editor...guidelines.htm
Trumped up crises such as Ferguson or the Garner cases, must not go to waste. They provide more and more reason, in the consciousness of the public, for Federal incursion and influence in all governmental areas, including policing,