Dick Morris theorizes that the White House halted the Republican Senate's use of the "nuclear option" to end judicial filibusters. If so, the White House is either incredibly dumb or incredibly wily.
It's ridiculous to let the Democrats' procedural rewrite of the Constitution go unchecked. Throughout history, Congress and the Presidency have had battles over their respective powers and the President must ensure that what few powers he has in the Constitution are zealously defended. Congress can afford to cede some power on the edges of certain areas if it so chooses because its enumerated powers are more clearly spelled out.
But the White House may be making two calculations: the first is Morris' theory that breaking the judicial filibuster will allow the Left to demagogue the judicial appointments Bush makes and scare women, minorities and independents from voting Republican in 2006 and 2008; second, is my alternative theory -- that the White House has a credible belief that it can increase the Republican majority in the Senate in 2006 and is working to do just that, especially against powerful Democrats in Red States (North Dakota, West Virginia, Florida; note that the White House likely won't target Ben Nelson of Nebraska), weak Democrats in barely blue states (Minnesota, Wisconsin, New Jersey) and weakened-by-events Democrats in other blue states (Michigan, Washington). That is a risky calculation, especially considering that two Republicans are likely to have difficult re-election campaigns (George Allen in Virginia; semi-useless Rick Santorum in Pa.). But the White House is known for gambling, and winning.