I believe the general manipulation of markets we are seeing now will be traced back to Robert Rubin who formulated a principle of financial activism, or intervention before the fact, as being cheaper and more effective that repairing markets after they suffer a significant decline as Greenspan had done in 1987.
As you may recall the 1987 experience led Reagan to form the President's Working Group on Markets, which grew into the infamous 'Plunge Protection Team' of the 1990's which made generous use of the Exchange Stabilization Fund, an opaque kitty used for general market tinkering.
Treasury Secretary Rubin's favorite tool of choice in the markets was said to be the SP futures since they carry the best 'bang for the buck.'
Apparently LIBOR is quite good on the interest rate side of things as well.
