They're stuck -- this is not just a Dan Rather thing, it's institutional. And they did it knowingly, and they can't not have known.
If they admit this, Dan Rather is out. Don Hewitt is out. 60 Minutes is dead. CBS News is exposed for the biased, Democrat-supporting organization we all know it to be.
Had they fessed up on day 1, they might have scraped by. But now they're stuck. They can't admit it, or they're ruined. So, in the inimitable words of Bill Clinton, they "just have to win."
This is encouraging to see. As factions of the Democrats behave like this, it's a sign of disarray. It's clear Rather and CBS are forced to try to save their own hide at long odds, against the interests of the larger movement (like a stock market crash). The movement would rather they eat a little crow and cut the losses, but they can't enforce it.
This is a symptom of the decay and lack of leadership of the Dem movement. The Clintons may think they have control of the situation, but their vehicle is careening at the moment.