NBC interrupted its regular programming to announce Russert's death, and in the ensuing moments, familiar faces such as Tom Brokaw, Andrea Mitchell and Brian Williams took turns mourning his loss.
Williams called him "aggressively unfancy."
Russert, of Buffalo, N.Y., took the helm of the Sunday news show in December 1991 and turned it into the nation's most widely watched program of its type. His signature trait there was an unrelenting style of questioning that made some politicians reluctant to appear, yet confident that they could claim extra credibility if they survived his grilling intact.
He was also a senior vice president at NBC, and this year, Time Magazine named him one of the 100 most influential people in the world.
Russert had Buffalo's blue collar roots, a Jesuit education, a law degree and a Democratic pedigree that came from his turn as an aide to the late Sen. Daniel Patrick Moynihan of New York.
One of his books, "Big Russ and Me," was about his relationship with his father.
He was married to Moureen Orth, a writer for Vanity Fair Magazine. The couple had one son, Luke.
Carl P. Leubsdorf, president of the Gridiron Club, an organization of journalists, said in a statement, "It was a measure of the degree to which Tim Russert was respected in the journalistic world that he was the first broadcaster elected to membership in the Gridiron Club after the rules were changed in 2004 to end our century-old restriction to print journalists."
"He was an enthusiastic member and a willing participant in our shows. His fellow Gridiron members join with all of those who knew and respected Tim in mourning his untimely death."
"Tim will be sorely missed because his years as Senate staffer and probing TV journalist gave him special insights on political and governmental issues," said Sen. Arlen Specter, R-Pa. "Had he chosen law as a career, his cross-examination would have made him a star in that field as well."