(CNN) - Former Sen. George McGovern urged Hillary Clinton Wednesday to drop out of the Democratic presidential race.
McGovern, who had endorsed Clinton, told CNN he was switching his support to endorse Barack Obama.
“It certainly was not out of any less respect for Senator Clinton,” McGovern told CNN in a telephone interview early Wednesday afternoon about his decision to switch his support to Barack Obama. “I think she has waged a really courageous and valiant campaign. She will have my affection and admiration for all of my days.
“But I think mathematically the race is all but won by Barack Obama and the time has come for all of us to unite and get ready for the general election in the fall.”
McGovern also told CNN he had just spoken to former President Bill Clinton about his decision to back Obama – a conversation he described as “very good.”
“I have had many conversations with him over the years, none better than today," McGovern said. "He did me the honor of talking to me about this. There will be no hard feelings with him or Senator Clinton.”
McGovern said he has not spoken to Sen. Clinton today, because he thought she would be too exhausted after Tuesday’s primary but plans to talk to her in the future.”
McGovern is not a Democratic superdelegate, though he is the first major Clinton supporter to publicly suggest the New York senator should abandon her presidential bid following Tuesday night's results.
Responding to the news, Clinton spokesman Mo Elleithee said "Senator Clinton appreciates Senator McGovern's friendship, but believes the voters in the upcoming states should have their voices heard in this process."
McGovern formally endorsed Clinton last October, saying then, "I think that if we can elect her president, she'll be a greater president even than her brilliant husband."
McGovern is a longtime friend of both Clintons and his decision is a personal blow to the New York senator and her husband. The couple's long political career has its roots in McGovern's 1972 presidential campaign, during which both Clintons were dispatched to Texas to run the candidate's operation there.
McGovern also remains a popular figure in the Democratic Party and especially in the State of South Dakota, which holds its primary June 3.