Kos has a post about how the NRCC, the Republican version of the DCCC, just threw $600,000 into the South Dakota June 1 special election race. This should give us a bit of insight into why the party groups - the DNC, the DCCC, the DSCC - are so important. They can provide the element of surprise in any campaign, providing the money for a sudden ad buy.
While giving to candidates is important, it's also important that the party machinery has a war chest that it can deploy where and when it decides.
