I remember posting this about three years ago on another thread, and I still stand by it:
"President Gore, just like President Clinton before him, weakened this country by crippling our national defense. This directly led to the 9/11 terrorist attacks, in which three thousand innocent civilians died. Had the Republicans been in the White House, there could never have been a foreign attack on American soil! And now, President Gore continues to undermine our national security by refusing to address the very real threat of Saddam Hussein's Iraq -- a known sponsor of world terror.
"In November 2004, vote for a man who will be tough on national security. Vote for a man who has experienced combat and served his country in uniform -- a war hero, who spent five and a half years as a prisoner of war. This November, vote for John McCain for President!"
I can picture McCain winning in 2004 over Gore. The Republicans will be merciless in blaming Gore and Clinton for 9/11 -- with the economy almost certainly still good that's all they've got going for them, but it's a powerful attack. And after all, McCain had his reputation as a moderate maverick -- that should swing some of the more conservative Democrats or Democratic-leaning voters, given that McCain would be perceived as "not so bad" as Republicans go. Cue Iraq invasion, two years later than OTL.