WASHINGTON - President Bush said Friday that Sen. Hillary Clinton, a potential candidate for the Democratic presidential nomination, is "formidable," but he declined to speculate on which Republicans might run for the White House in 2008. "This is an unusual year because this is the first time there hasn't been a kind of natural successor in the party," Bush said in an interview with "CBS Evening News." "Two wide-open primaries with no sitting vice president running in either primary, so this is — I can't remember a time when it's been this open." In a wide-ranging interview at the White...