Party strategists say it's very important for McCain to stay close. If he were to emerge from the convention 10 points down to Obama, it would be a sign that Republicans are in a world of hurt.
At the moment, that seems unlikely. A better bet is that the presidential race will settle back close to where it was before the conventions, a virtual tie.
Make the case for a McCain presidency
The final, and perhaps most important, task tonight is to clearly define McCain's candidacy - and by extension what a McCain administration would be about.
In 2000, the last time the presidency changed hands, Republicans campaigned on a forward-looking theme: restoring respect and dignity to the White House after Bill Clinton's years in office, which were marred by personal scandal and impeachment.
Ken Khachigian, a White House speechwriter in prior Republican administrations, said he would like to see McCain sum up his candidacy in a couple of sentences.
"I think he's defined himself, but he's done it sort of scattershot. He needs to be giving a compelling reason for him to become president," said Khachigian, who played an active role in McCain's 2000 primary fight against Bush.
"I don't think it's the agenda," he added. "It's the overarching connection with the American people."
