To rely on moderates as your base is like building on quicksand, since moderates are rarely ever loyal to any one candidate, and are less likely to even show up and vote anyhow. The polls in the run up to the election bear this out. When it came to registered voters, Whitman did quite well in the polls. But among likely voters, her lead shrunk considerably. It was exactly the opposite in this race because the ideologically rootless and moderate Whitman supporters did not show up at the polls.
Moderates are an especially weak and unreliable base.
While it is necessary to appeal to moderates, doing so at the expense of securing your base is a grave mistake indeed. This almost cost Whitman her job - and it probably cost her her political future. Whitman's collosal blunder was to ignore and disdain her conservative supporters. This is not the spin you will hear in the media, however. The media will tell you that the Republican Party is essentially divided and that the Right was holding Whitman a political hostage.