This has to be an emotional whirlwind for Barack and his family -- to be on the verge of the biggest night of their lives and to lose a loved one.
(CNN) -- Sen. Barack Obama's grandmother, Madelyn Dunham, has died following a bout with cancer, Obama and his sister, Maya Soetoro-Ng, said Monday.
She was 86.
"She was the cornerstone of our family, and a woman of extraordinary accomplishment, strength, and humility," their statement said.
"She was the person who encouraged and allowed us to take chances. She was proud of her grandchildren and great-grandchildren and left this world with the knowledge that her impact on all of us was meaningful and enduring. Our debt to her is beyond measure."
Obama and Soetoro-Ng asked that donations be made for the search for a cure for cancer in lieu of flowers. A small private ceremony will be held "at a later date."
Dunham passed away peacefully at her home shortly before midnight Sunday night (5 a.m. ET), campaign spokeswoman Jen Psaki told CNN. She said Obama learned of her death around 8 a.m.