By Jill McGivering
BBC News, Washington DC
The message stays the same, but in this final, crazy week of campaigning, the style is slowly changing and, most days, so do the celebrities.
Senator John Kerry is making a mad dash, criss-crossing the United States to hit the closest marginal states and whip up support.
It started with a bang in Philadelphia on Monday.
Tens of thousands of supporters waited all morning for a glimpse of former President Bill Clinton - his first appearance in public since heart surgery last month.
Springsteen was the latest of a number of celebrities to back Kerry
The hysteria in the crowd made it feel more like a rock concert than a political rally.
I saw women of all ages jump, scream, faint and collapse in tears as Bill Clinton endorsed Senator Kerry.
There was no doubt about Bill Clinton's popularity, but it was not clear how much of his famous charisma was rubbing off on the senator.
Many turned to leave when President Clinton finished and the senator began to speak.
Senator Kerry has been criticised for an uninspiring monotone delivery and stiffness with crowds that some see as elite or aloof.
The contrast with Bill Clinton's easy warmth did not help.
On Tuesday, it was Las Vegas - a subdued, smaller gathering in a park in the city's outskirts, a family affair with children dressed in Spanish costume and toddlers perched on shoulders for a better view.
This time the celebrity was rock chick Sheryl Crow with her gentle protest lyrics calling for change.
Senator Kerry had flown almost the width of the United States for this small suburban rally. He looked tired and a little wooden, as if the Clinton charisma had already evaporated.
KEY SWING STATES
1. Florida - 27 electoral votes
2. Pennsylvania - 21
3. Ohio - 20
4. Minnesota - 10
5. Wisconsin - 10
6. Iowa - 7
7. Nevada - 5
8. New Mexico - 5
9. New Hampshire - 4
But Thursday's extravaganza came as an explosion of energy.
About 80,000 people, 12 blocks deep, packed together in Madison, Wisconsin, for one of the biggest rallies local people said they had ever seen here.
The size of the celebrity helped - this time it was rock star Bruce Springsteen, known as "The Boss", whose hit No Surrender is the Democrats' campaign theme song.
Senator Kerry seemed a changed man, punchy where he had been long-winded, energised where he had been flat and just far more human.
He even risked jokes: "When George Bush heard I was appearing with The Boss, he thought it was Dick Cheney."
Getting the voters out
Some of the people we spoke to were already loyal Democrats.
But John Kerry's challenge here is to make sure both that Democrats get out to vote and also to win over undecideds.
The rock rally did seem to capture at least some.
We spoke to one die-hard Springsteen fan who said that, until a week ago, he was undecided. Now he was voting for Kerry.
"It's a strange mix: rock'n'roll and politics," he said, "but it blended well today. It's pretty impressive."
The substance does not change. At every rally, Senator Kerry lambasts President Bush for his handling of Iraq, raises the controversial missing explosives as evidence of mishandling and says the US is now less, not more, safe.
He emphasises the economy - the increase in job losses, tax cuts to wealthy elite and outsourcing under the Bush administration.
His own message is all about more jobs, better health care, no privatisation of social security and progress on stem-cell research.
After a few days, it all sounds very familiar, but his audience is constantly changing and Senator Kerry is hammering home his core message.
In the course of this week, his performance has changed.
It is hard to know what that signifies - and whether it will lead to triumph or disappointment - but there is a feeling of gathering momentum and expectation in this campaign, not least because Senator Kerry is learning how to engage and rally a crowd at last.