"I appreciated his reminder that we can disagree while still being respectful of each other," Obama told thousands of supporters at the first of four outdoor rallies in Philadelphia.
"Sen. McCain has served this country with honor," he said two hours later, in the city's Germantown neighborhood. "He deserves our thanks for that."
At a town-hall event Friday in Minnesota, McCain took the microphone from a woman who said Obama is an Arab. McCain said, "No, ma'am," and he called Obama "a decent, family man."
McCain drew boos at the same event when he told a supporter who expressed fear at the prospect of Obama's election that the Democrat is a "person that you do not have to be scared of as president of the United States."
Those reassurances aside, McCain's TV ads continue to attack Obama sharply. Some hit his ties to a former radical who co-founded a violent anti-war group in the 1960s. Yet on Saturday at an event in Iowa, McCain didn't mention the past association and focused on their policy disagreements.
Obama referred to the ads Saturday. "We've seen rough stuff on the TV from them," he said. "I can take it for four more weeks," but the nation cannot take "four more years of Bush-McCain economics."
"I will be a president who puts you first," he said, asking voters not to lose hope in the economy before President Bush can be replaced.
Polls show Obama leading in several battleground states, and some of his top surrogates feel victory is nearly in reach.
"The one thing we can't let happen is for us to be overconfident," Pennsylvania Gov. Edward Rendell told donors at a Friday fundraiser, where he introduced Obama.
Although Obama says anything can happen in the campaign's final 24 days, hints of his optimism are creeping into his unscripted remarks.
"In some ways this is a celebratory event" as "we're now coming to the end of what has been a two-year process, an extraordinary journey," Obama said at a second Philadelphia fundraiser Friday night. The host, Comcast executive David L. Cohen, said the two events raised more than $5 million.
As 250 major donors ate beet salad and mahi-mahi under a huge tent, Obama seemed to look ahead to his first term as president.
"We're going to have to make some priorities, we're going to have to cut some things out," he said, referring to expensive goals such as improving health care, schools and college affordability.
"I'm going to be in some fights with my own Democratic Party in getting some of that done," he said.
Defying tradition in GOP-leaning states, he said, he is leading McCain in Montana and North Carolina. His lead in Virginia, which Democrats last carried in 1964, is 6 or 7 percentage points, he told the donors.
Obama added, however: "Who knows what can happen in the next 25 days?"
Democrats have carried Pennsylvania in recent presidential elections, although sometimes narrowly. McCain has campaigned aggressively in the state, but polls show Obama leading.
Democrats usually win huge margins in Philadelphia and try to minimize their losses in the state's smaller cities and more rural areas. Obama's barnstorming of Philadelphia was designed to drive his base's vote as high as possible.
Under a brilliant blue sky, thousands turned out at each spot. In some cases, thousands more were unable to get through the gates. They stood on cars and craned their necks for a glimpse, sometimes blocks away. Crowds cheered Obama's motorcade as it arrived and left each site.
Obama read the same speech each time, but he ad-libbed a bit and seemed increasingly buoyant as the day progressed. Telling his favorite new story about buying pie from a Republican-leaning Ohio diner owner, he joked with a woman who called out from the Germantown crowd.
"You will make me some pie?" he asked. "What kind of pie do you make? Sweet potato pie?"
As the crowd roared, he poured it on. "We're going to have to have a sweet potato pie contest," he said. "I'll be the judge, because I want my sweet potato pie."
On the Net:
Obama campaign: http://www.barackobama.com/index.php
McCain campaign: http://www.johnmccain.com/