The curious part is that Obama keeps saying just the opposite: Not one thing is sealed.
"We can't afford to slow down, or sit back, or let up, for one day, for one minute, for one second in this last week," the Democratic presidential nominee told supporters Thursday.
"Not now. Not now," Obama said in the Florida sunshine. "We've got to work hard."
For a range of reasons - the slippery nature of polls, the Democrats' history of heartbreak, the still-to-be-determined effect of race, the desire not to jinx himself - Obama is, in fact, working the vote hard.
In his race against Republican John McCain, Obama has gone big, drawing hundreds of thousands of people to rallies in the last few days alone. He used his fundraising muscle to buy a prime-time TV slot for his infomercial, viewed by 33.6 million, and touted his new unity with former President Clinton.
But Obama also is careful to look engaged individually, too. Twice this week, in campaign offices outside Denver and in Pittsburgh, he got on the phone directly with voters.
One woman grilled him at length about his environmental record. One said she wanted tickets to his inauguration. One made him smile by saying she was 100 percent Obama.
"I won't let you down," he told her.
It is standard election politics not to look cocky. Voters hate being taken for granted. Yet the tone of Obama's argument suggests he is going beyond playing it safe.
Despite all the polling pointing in his favor, there remains a feeling in his campaign that anything can happen at the end. Obama appears easy and unworried - he even took time Thursday to visit a pumpkin patch - but signs and words of overconfidence are shunned.
"Complacency kills campaigns," said Mark Mellman, a Democratic strategist and John Kerry's pollster during the 2004 presidential race. "Winners always run like they are behind."
That helps explain why Obama barreled on with an outdoor rally in Pennsylvania this week despite the foul weather. The thousands of people who showed up endured sideways rain, cold chills and mud. McCain canceled a similar rally 50 miles away.
Obama told them: "If we see this kind of dedication on Election Day, there is no way that we're not going to bring change to America."
Late come-from-behind wins are rare in presidential races.
In Gallup polling, only twice in the past 14 elections did a candidate lose the popular vote after being ahead about a week before the election. They were Democrat Jimmy Carter in 1980 and President Bush in 2000, although he won the electoral vote.
As the election closes in, Obama leads McCain in most national polls, and most state surveys show him running strong in traditional Democratic states and leading in some that Bush won in 2004, including Ohio, Colorado, Nevada and Virginia. That makes a path for a McCain victory difficult to discern.
Mellman said all those polls assume that every Obama supporter will turn out to vote, and that every volunteer will do what it takes to turn out the vote.
"Don't believe for one second in these polls," Obama told a crowd of 35,000 people outside Orlando, Fla., late Wednesday night. "Power concedes nothing. We are going to work over the next five days like our lives depended on it. We're going to have to struggle."
When Obama talks of that election struggle, others have a hard time believing. His consistent lead in the polls has even become part of the late-night TV comedy conversation.
Craig Ferguson of CBS' "Late Late Show" put it this way: "Obama is so far ahead now, seems the only way he can lose is if his supporters screw it up. But aha! Obama's supporters have a secret weakness: They are Democrats."
One way to look at Obama's approach is that he's not just running to win. He's trying to sweep every single state in play, giving him and his party a crushing win and big leverage. A more sober reading is that Obama has already learned one humbling lesson this year.
He scored a surprise victory in the Iowa caucuses and then, while riding high, promptly lost the New Hampshire primary to Sen. Hillary Rodham Clinton.
"The great thing about having run for 21 months is we know from hard experience that you shouldn't take anything for granted," Obama adviser David Axelrod said in an interview.
"We've been ahead and we've been behind," he said. "Sometimes we've assumed that when we're ahead - New Hampshire is a big example - that that guarantees anything. It doesn't."