"I considered him not only a journalist but a friend," Obama said. "There wasn't a better interviewer on television, a more thoughtful analyst about politics."
The Democratic hopeful added that Russert was "one of the finest men I know. I am grief-stricken with loss and my thoughts and prayers go out to his family."
McCain and his wife Cindy also issued a statement following the death of Russert at age 58 of coronary artery disease.
"I am very saddened by Tim Russert's sudden death. Cindy and I extend our thoughts and prayers to the Russert family as they cope with this shocking loss and remember the life and legacy of a loving father, husband and the preeminent political journalist of his generation," said the Republican candidate.
"He was truly a great American who loved his family, his friends, his Buffalo Bills, and everything about politics and America. He was just a terrific guy," McCain continued. "I was proud to call him a friend, and in the coming days, we will pay tribute to a life whose contributions to us all will long endure."