As the serious stage of the presidential campaign begins this fall, Hillary Clinton has clearly established herself in the lead of the race for the Democratic nomination. That makes her the most worthy subject for examination among all the White House prospects. I have been thinking a lot about Sen. Clinton, because part of my vacation reading was Carl Bernstein's fine political biography of her, "A Woman in Charge," published earlier this year. Its 600 pages, carefully reported and written with a commendable evenness of tone, offer perhaps the fullest portrait of this potential president. The single strongest impression it...