Democratic Sen. Paul Wellstone, his wife Sheila and daughter Marcia died Friday in a small plane crash near Eveleth, Minnesota, Democratic sources said.
The sources said three staff members and two crew members also died in the crash.
The plane went down in a wooded area about 7 miles east of Eveleth-Virginia Municipal Airport. Officials said bad weather was reported in the area, and the last contact with the plane was at 10:20 a.m. CDT when the plane was about 2 miles from the Eveleth airport.
Choking back tears, a Senate colleague expressed his sympathy. "He was such a good man, and his wife too," said Sen. Patrick Leahy, D-Vermont. "All of these people had families and they had friends and this is a horrible, horrible thing."
Such sentiments were echoed by Republicans: "He always just had a love for every person because you knew everything that he was talking about he deeply believed in and deeply cared about," said Sen. Sam Brownback, R-Kansas. "And then he cared deeply about the people around him. He was a very engaging person."
From his ranch in Crawford, Texas, President Bush called Wellstone "a man of deep convictions. He was a plain- spoken fellow who did his best for his state and for his country."
The president offered "prayers and heartfelt sympathy" to the Wellstone family and the families of the other people who died in the crash.
Wellstone held a key Democratic seat in the U.S. Senate and had been criss-crossing the state in a tough re-election campaign against former St. Paul Mayor Norm Coleman.
The plane, a twin-engine turboprop King Air manufactured by Raytheon Aircraft, took off from Flying Cloud Airport in Eden Prairie, a southwestern suburb of Minneapolis. He was scheduled to attend a funeral in the northeast, followed by a campaign stop in Duluth.
Wellstone, 58, won his Senate seat in 1990, the only challenger that year to unseat an incumbent.
The son of Russian immigrants, Wellstone was raised in Arlington, Virginia, and was a champion wrestler at the University of North Carolina in Chapel Hill, where he earned both a bachelor's degree and a doctorate.
The charismatic Wellstone, who had multiple sclerosis but was not incapacitated by it, was a champion of health care coverage expansion, veterans affairs and environmental concerns, and was considered by many to be one of the Senate's most liberal members.
His death leaves a void in the state's election for the Senate.
Under Minnesota law, if a nominee in a Senate race dies during a campaign, his or her political party can select a replacement candidate no later than four days before the general election. Election Day this year is November 5.
The Republican National Committee had shown a strong interest in defeating Wellstone.