MDC-T spokesman Douglas Mwonzora told SW Radio Africa that Makumbe, who was a key member of his party, died at Arcadia Medical Centre in Harare on Sunday morning after suffering a suspected heart attack.
He is survived by his wife, Virginia, and five children.
Late last year, the University of Zimbabwe professor announced he was going to take a break from teaching to contest in the forthcoming general elections as an MDC-T candidate for Buhera West constituency in Manicaland province.
He told SW Radio Africa, shortly after his announcement last November, that he had been, "doing a lot of talking and now it is time to show that I can also walk the walk."
Makumbe said: "There are various ways of emancipating Zimbabwe from the tyrannical system of government we have endured under ZANU PF. You can either make noise from your white castle or you can put on your boots and overalls and fight for the emancipation of the country."
Mwonzora said Makumbe was a "hero of the democratic struggle" in Zimbabwe and the MDC-T owes the success of the constitution making process to his wisdom as he was the technical adviser for the party.
Tributes are pouring in for the man who many have described as "a rare voice of sanity" in Zimbabwe.
Journalist Farai Sevenzo said: "Makumbe was a rare act - a walking talking thinking advert against prejudice and tyranny.
He had a forensic analytical mind that came with charm and a disarming sense of humour, which made the task of interviewing him never boring. A big loss."
Zimbabwean Glen Mpani said, "Professor's commitment to a free Zimbabwe was unquestionable. His untimely death before achieving what he dedicated his life for, should spur those who remain to make his dream a reality."
Zimbabwe Lawyers for Human Rights director Irene Petras said: "The white man from Buhera has gone too soon."
"He was one of the few outspoken voices of conscience remaining in the academic community and a much loved member of the civil society. His wit, intellect and humour ensured that he and those around him were able to survive troubled times and remain resolute to the struggle for a better Zimbabwe."