Baron, whose link to the John Edwards mistress scandal this summer put him in an unwanted spotlight, died following complications of cancer, said Harrison Hickman, a family spokesman.
"Fred's life was too short but he lived it to the fullest," the Baron family said in a statement. "We will miss his spontaneous smile, his good humor, his sharp mind and his loving heart."
Baron had been diagnosed with multiple myeloma. His death comes just two weeks after he obtained an experimental cancer-fighting treatment following a public plea by his son, Andrew, who had called the drug Tysabri his "last chance effort for life."
Boston-based Biogen Idec Inc. had refused Baron access to the drug despite prominent figures such as former President Bill Clinton and cyclist Lance Armstrong pushing the drug maker on Baron's behalf. The company had maintained the regulatory risks of giving Baron the drug were too great.
It was the second time Baron made national news in the past few months.
In August, Baron made headlines when he acknowledged sending money to the former mistress of Edwards, the former Democratic presidential candidate. Baron had been the national finance chairman for Edwards' presidential campaign, and had said Edwards had no involvement with the payments.
Those payments were used to resettle Rielle Hunter, Edwards' mistress, in California.
But Baron's biggest legacy will be his tort litigation and fundraising for Democrats. He bankrolled millions for Democratic candidates in Texas, almost single-handedly rescuing the party from financial catastrophe.
"A fierce advocate for those who believed they had no voice, Fred made it his life mission to protect and defend those who needed the most help," state Democratic Party Chairman Boyd Richie said in a statement. "A true champion of the people, Fred's presence will be profoundly missed."
Records show that just since the 2006 elections, Baron and his wife, Lisa Blue, have contributed some $2 million to Democratic candidates and causes. His fundraising helped launch the Texas Democratic Trust, which helped the party make influential gains statewide.
"Fred was a wonderful, generous and optimistic man who inspired so many people not only to help their party, but to help their country and their state," said Matt Angle, director of the Texas Democratic Trust.
Funeral services were expected Monday.