"To announce that there must be no criticism of the president, or that we are to stand by the president, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public." Theodore Roosevelt
The president's "argument" for her amounts to: Trust me. There is no reason to, for several reasons.
He has neither the inclination nor the ability to make sophisticated judgments about competing approaches to construing the Constitution. Few presidents acquire such abilities in the course of their pre-presidential careers, and this president particularly is not disposed to such reflections.
Furthermore, there is no reason to believe that Miers's nomination resulted from the president's careful consultation with people capable of such judgments. If 100 such people had been asked to list 100 individuals who have given evidence of the reflectiveness and excellence requisite in a justice, Miers's name probably would not have appeared in any of the 10,000 places on those lists.
In addition, the president has forfeited his right to be trusted as a custodian of the Constitution. The forfeiture occurred March 27, 2002, when, in a private act betokening an uneasy conscience, he signed the McCain-Feingold law expanding government regulation of the timing, quantity and content of political speech. The day before the 2000 Iowa caucuses he was asked -- to ensure a considered response from him, he had been told in advance that he would be asked -- whether McCain-Feingold's core purposes are unconstitutional. He unhesitatingly said, "I agree." Asked if he thought presidents have a duty, pursuant to their oath to defend the Constitution, to make an independent judgment about the constitutionality of bills and to veto those he thinks unconstitutional, he briskly said, "I do."
The crowning absurdity of the president's wallowing in such nonsense is the obvious assumption that the Supreme Court is, like a legislature, an institution of representation. This from a president who, introducing Miers, deplored judges who "legislate from the bench."
To that I say: What do you expect? A stupid is, a stupid does. You voted for him. Suck it up.