Miers wasn't a disaster, she was bait and a feint. Think about it this way:
Miers is unqualified for service in the Supreme Court; Bush asks her if she'd be willing to be nominated and serve as bait for the Dems, knowing that she wouldn't possibly be confirmed. She agrees.
The nomination is made; Dems show their true obstructionist colors and expend enormous amounts of political and financial capital to try to stop Miers being ramrodded through the Senate.
Bush pulls the rug out from under them by announcing the (planned from day one) withdrawal of Miers, followed by naming the *real* nominee, Alito.
This leaves the Dems with little capital *or* general support among the populace to obstruct the Alito confirmation process *and* weakens them further.
Don't *ever* play poker with President Bush. The Dems still haven't learned this; pray that they never do.
This is certainly my preferred way of looking at it. President Bush has shown himself several times to be far cannier than he appears.