"one big problem with that is the political issues involved"
If you say "superheavy SSTO" in 2006, there's more big problems than politics alone.
MSTO is "extremely" efficient, and SSTO can only be more efficient if it is done very, very good. We can't even do it bad at the moment, apart from so bad that it doesn't work. Throwing off stages ahlfway is very efficient as you get rid of some dead mass. THe penalty is the extra mass of subsequent engines. The lack of throwing out dead mass halfway in SSTo needs to be smaller than the gain in not carrying extra engines. We're not there yet by far.
The ultimate in efficiency would be continuous burn to orbit: a self-eating rocket that leaves no useless mass after part of the fuel has burned off, but keeps the engine working. Think of a solid fuel rocket in which there is no fuel tank whatsoever, and somehow the flame can still be directed without there being an actual engine, just burning. That kind of idea
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