Josh Marshall hints at this, but one of the key variables in whether a damaged nominee survives is presidential support. So far, Obama has been aggressive in his support of Daschle. In part, that may be his view of the merits of the case. But it's worth keeping in mind that Daschle isn't an ordinary nominee. In certain ways, he's Obama's political godfather. To that end, Daschle occupies a unique role in Obamaland, which I describe in more detail here.
