Per my post below, this is over before it begins. Roberts was approved by unanimous consent on the Senate floor in 2003 after passing the Judiciary Committee on a 16-3 vote. Given that he just went through the confirmation process, it's extremely unlikely that anything will turn up that would allow the Democrats to defeat him, but I'm sure we'll hear lots of hysteria from the liberal interest groups anyway.
The pick is interesting from another angle, however. As Ed Kilgore noted, Roberts served as deputy solicitor general under Bush I, was nominated for the federal bench by Bush's father, and served as an adviser to Jeb Bush during the Florida legal battle in 2000. Bush appears to view a track record with him and his family as an acceptable way to demonstrate one's bona fides (see Dick Cheney, Alberto Gonzales, Colin Powell, Margaret Spellings, etc.) -- part of his general tendency to favor loyalty and machine politics over doctrinaire conservatism. Roberts was not the top choice of DC conservatives, but he has a history of loyal service to the Bush family and he's likely to be confirmed at little political cost. It fits the pattern.
Update 7/21: This post was updated to clarify that Roberts advised Jeb Bush, not George W., during the Florida legal battle.
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