HONOLULU - For the last 21 months, she has followed the odyssey of his presidential campaign like a spectator in a faraway balcony.

Nearly blind, she underwent a corneal transplant to see him on television. She reluctantly agreed to film a political ad when he needed to reassure voters about his distinctive American roots. She told him that it might not hurt if he smiled a bit more.

On Friday, Barack Obama -- a grandson, not a candidate -- spent the day saying goodbye.

He came to the Punahou Circle Apartments, a place of his childhood, where his grandmother Madelyn Dunham, who turns 86 on Sunday, lay gravely ill. For weeks, while not mentioning her illness while campaigning, he has talked to doctors and tracked her condition. After she was released from the hospital last week, he received word that he should not wait until after the election to make what he believes could be his last visit.

It was an unusual departure from the tug-of-war of a presidential campaign, particularly with 11 days remaining in the race. But it was a trip that his advisers said he told them was not negotiable. He missed his mother's death in 1995, a mistake he said he did not intend to repeat with his grandmother, who helped raise him and has been a stalwart force in his life.

"My grandmother's the last one left," he said. "She has really been the rock of the family. ... Whatever strength and discipline that I have, it comes from her."

His first visit lasted about 70 minutes on Thursday evening. He returned on Friday to the 10th floor apartment -- the place he lived between ages 10 and 18 -- which was flooded with flowers and well wishes from strangers who were introduced to her in Obama's first book, "Dreams From My Father."

Obama has reached the closing days of his run for the White House without holding a formal biographical tour. (In a candidacy built on biography, and criticized for its celebrity, his advisers believed that sticking to substance was a wiser course.)

But suddenly a biographical tour unfolded around him, as he visited the woman who was a guiding force in his life and played a supporting role in his candidacy, from the Iowa caucuses to his marquee speech on race in Philadelphia and to his general election effort to win over voters in red states.

The moment Obama stepped off the plane late Thursday evening, after a nine-hour flight from Indianapolis, his motorcade drove directly to the 12-story apartment building on South Beretania Street. His return to Hawaii was covered live on the local news, but his arrival was subdued. He did not wave to the cameras.

"Without going through the details too much, she's gravely ill. We weren't sure, and I'm still not sure whether she makes it to Election Day," Obama told ABC's "Good Morning America" in an interview aired Friday. "She's still alert and she's still got all her faculties. And I want to make sure that I don't miss that opportunity."

As Obama flew west across six time zones, he stayed in the secluded front cabin of his campaign plane. He read, slept and briefly talked with aides, but he kept his distance from reporters who accompanied him.

It was a starkly different mood from that of Obama's pilgrimage to Kansas nine months ago for his first visit to the town of El Dorado, where his grandparents originally lived.

"She can't travel," Obama said of his grandmother in late January. "She has a bad back. She has pretty severe osteoporosis, but she's glued to CNN." A smile washed over his face as he spoke about the woman he calls "Toot," his own shorthand for grandparent, which in Hawaii is Tutu.

Back then, when Obama was in the opening stages of his Democratic primary fight, he spoke wistfully about his grandparents, whose all-American biography had become critical to establishing his own American story. He told of how his grandfather, Stanley Dunham, fought in World War II while his grandmother worked on B-29s at a Boeing plant in Wichita.

"My grandparents held on to a simple dream, that they would raise my mother in a land of boundless dreams," he said. "I am standing here today because that dream was realized."

It is that story that has played a recurring role in TV commercials during Obama's race against Sen. John McCain. As the two debate over taxes and spending and health care plans, these biographical ads are intended to serve as a validation to answer the other lingering questions about Obama's candidacy.

In only one commercial can Dunham be heard speaking. It was taped before the Iowa caucuses, but also replayed during the Pennsylvania primary, as Obama sought validation for his appeal to older women voters. Her osteoporosis was advanced, and she hunched over so severely that it was difficult for filmmakers to capture her spirit and words of support. Only a few seconds of tape was used.

In August, as Obama prepared to accept the Democratic nomination, he delivered a long-distance message to his grandmother in a televised speech. "Thank you to my grandmother, who helped raise me and is sitting in Hawaii somewhere right now because she can't travel, but who poured everything she had into me and who helped to make me the man I am today," Obama said. "Tonight is for her."

The Washington Post and Associated Press contributed to this report.