Rudolph W. Giuliani leads the race for the GOP presidential nomination, with Republican voters describing him as the field's strongest leader and most electable candidate in the 2008 general election, according to a Washington Post-ABC News poll. But the Republican contest remains unsettled just three months before the first votes will be cast, and in comparison with fellow New York politician Hillary Rodham Clinton, Giuliani is a far less solid front-runner. He has double the support of his nearest rival, but a majority of those who support him do so only "somewhat." At the same time, his advantages on key...