KEY POINTS:
Nothing raises the spirits of the party faithful like a barnstorming convention speech, and Sarah Palin's on Wednesday night was by any standards a stem-winder.
The problem is that convention speeches have a very short shelf life.
Barack Obama, too, made a pretty decent speech when he accepted his party's nomination in Denver just eight days ago. But who remembers a word that he said?
It may be churlish to say so, but Ms Palinis terrific performance, which even Democrats grudgingly admired n may meet a similar fate.
Her speech contained nothing of policy substance. Its value lay less in its content than its galvanising effect on the conservative wing of the Republican party which has never embraced John McCain.
Conservatives had prepared for the St Paul convention in lacklustre spirits, fearful that Mr McCain might even pick as his running mate his old friend and apostate Democrat Joe Lieberman who, all other things being equal, would have been his first choice.
But Mr Lieberman, a pro-abortion moderate, would have provoked a rebellion among social conservatives. Now, in the pro-life and pro-gun Ms Palin, these latter have one of their own - and a ticket they can at last throw themselves behind wholeheartedly.
But will her selection prove to be a "game-changer", a development that turns on its head the entire campaign n as it enters the 60-day sprint to the finish line n on its head?
It is possible, but unlikely.
In a country with a thirst for novelty, Ms Palin fits the bill perfectly. She now has the very celebrity quality for which Republicans mock Barack Obama.
Her speech highlighted her youth and non-Washington background, a perfect foil for Mr McCain, a veteran Congressional insider who could be the oldest man ever to become president.
Remember however that she was speaking to the friendliest audience she will ever encounter - the most exciting new Republican star since Ronald Reagan, one party strategist gushed yesterday.
She had some good lines, none better than the way she drew the distinction between Messrs Obama and McCain, the former who had "used echange" to promote his career, and the Republican candidate who "used his career to promote change".
But even her lesser lines, including her gratuitously insulting reference to Mr Obama's work as a community organiser on the south side of Chicago, were guaranteed a rapturous reception in the hall.
Outside, it is another matter.
Conservatives have been enthralled. But will the same be true of die-hard Hillary Clinton Democrats, whom Mr McCain is trying so hard to win over?
And how will voters elsewhere respond to this daughter of Alaska, about the least representative of the 50 states?
Sarah Palin, one way and another, is still largely an unknown quantity for most Americans.
Good jokes at Mr Obama's thin resume cannot conceal her own lack of experience. The media scouring of Alaska for details about her has barely begun.
No one can be sure that new embarrassments will not emerge.
And one final thought. Every vice-presidential nominee has his or her moment in the headlines, but in the end they hardly matter.
Voters will be picking a president, not his number two. Dan Quayle, George HW Bush's running mate in 1988, was hapless.
Yet the older Bush trounced his opponent Michael Dukakis on election day.
- INDEPENDENT