Exactly. It is these candidates who are "going to find it difficult to keep up momentum". Palin will announce in her strategic time. People who seem to be swayed by the naysayers' anti-Palin campaign were never for Palin in the first place.
Strategy isn't the be all and end all. Emotional and ideological commitment is huge in politics. The longer she waits the more likely it is that this commitment to her by conservatives will transfer to other candidates. People WANT certainty.