The 2000 McCain campaign -- and the extra media money he used between New Hampshire and Super Tuesday -- peeled support away from Bush and exposed some of his machinations (for those who were willing to see through them). The result was fewer Bush votes in November.
You know how close November 2000 was. A little help in the right place might have changed the outcome (though the primary objective was to keep Bush off the Republican ticket).
Every day for years the netroots have advertised their innate inability to think in terms of the connection between actions and consequences. Democrats get out-played cycle after cycle.
We're doing it again. We don't have to, but we're doing it again.