That is the only way Presidents have made such a choice or COULD make such choices. It all boils down to who the President thinks he should nominate.
Well yes, but the problem with Miers is that what Bush sees in her is apparent to few of those who don't know her. That didn't have to be the case. He could have appointed many others whose fitness for the court would not have been questioned, especially by his own base. The trouble with Miers is that she's vulnerable to attacks on both ideology (murky) and cronyism, which combined may well be enough to kill her.