So there was a leak of an internal NASA document a few weeks ago which showed that space transportation architectures that employed the use of orbital storage of propellants, rather than lifting them all at once on a heavy-lift vehicle (such as the Senate Launch System), would save the taxpayer tens of billions of dollars and accelerate the schedule for manned trips beyond earth orbit by half a decade or more. It was information that California Congressman (and former Chairman of the Space Subcommittee) Dana Rohrabacher had been demanding from the agency for weeks, to no avail until it was leaked. The political effect would be that the SLS is unneeded, which would be a devastating blow to those senators and representatives who had continued to support it as an earmark for jobs in their districts.

Well, supporters of the "Big Monster Rocket" have struck back. Previous NASA administrator Dr. Michael Griffin, and former NASA associate administrator under him (and current head of the Space Policy Institute at GWU) Dr. Scott Pace, have jointly written an editorial defending it over at Space News. Despite the credentials and experience of the authors, however, the arguments presented are flawed

For a detailed analysis, see this article:

http://www.competitivespace.org/2011/11/04/the-sls-empire-strikes-back/