The Democrat senators are likely to weigh the nominee against their reelection hopes and will to power - and no doubt now perceive Bush as wounded, thus vulnerable. Therefore, I would fully expect them to beat Brown to a bloody pulp to convince their base that they are more powerful than Bush and the Republicans.
Janice Rogers Brown would be savaged, but perhaps her nomination and savaging would make a point that the president and Sen. Frist have been trying to get across for a couple of years now.
There are republicans, too many of them, who will jump ship if it comes to a nuclear option vote. The nominee will then fail.
I think we need to walk down that road to prove that point.