Weeks of practice, hours of going over prep manuals at the equivalent of Debate Camp have come down to this: An hour and half debate that has become the marquee event of the campaign.
Never before has the bottom of the ticket overtaken the top, and no detail has gone unnoticed, from the height of the podiums to how the candidates will be addressed.
The latest ABC News/ Washington Post poll show an uphill battle now for Republicans, specifically because of Palin.
Her favorability ratings have dropped 7% in the last five weeks. Fewer voters believe she has enough experience for the job, down 12% since last month. Biden's number is up.
19% more voters are less likely to support the GOP ticket because of Palin.
I talked to Connecticut Senator and former vice presidential candidate Joe Lieberman today. He says there are only three times a VP candidate matters during the race.
"Sarah Palin has really done brilliantly in those first two, the day she was announced and the acceptance speech," Sen. Lieberman said. "Now she's got to come out and change the discussion."
McCain told Action News he still backs his choice and thinks Americans will see Palin differently than how she's portrayed in the media.
"I'm very confident about her and she's sparked enthusiasm in this campaign like I've never seen before," Sen. McCain said.
Obama's camp says Biden will not exploit the new polls, but will play it straight.
"He's here to talk about his vision of the future, his vision that he shares with Barack Obama, his position on things like rebuilding the middle class," said Stephanie Cutter, Michelle Obama's Chief of Staff.
Before tonight, the most watched Vice Presidential debate was back in 1984 When George Bush squared off against Geraldine Ferraro.
Tonight's showdown in the "show me" state is expected to easily eclipse that in viewership.