May 7 (Bloomberg) -- Former Senator George McGovern is switching his support for Hillary Clinton in this year's race for the Democratic presidential nomination to Barack Obama, and he urged her to drop her bid so the party can unify behind one candidate.

McGovern said the time has come for the two top Democrats to stop fighting each other and for the party to begin preparing for the general election battle against the likely Republican nominee, Arizona Senator John McCain.

``We've got to start getting ready for McCain,'' McGovern said in an interview. ``This is a Democratic year unless we Democrats defeat ourselves.''

Speaking to reporters after she held a rally in Shepherdstown, West Virginia, Clinton, when asked about McGovern's announcement, said, ``I respect him and he has a right to make whatever decision'' he chooses.

McGovern, 85, was the Democratic presidential candidate in 1972 and lost to Republican Richard Nixon. New York Senator Clinton, 60, got her start in national Democratic politics in 1972 when she worked on McGovern's campaign while a law student at Yale University. Bill Clinton also worked on the McGovern campaign that year.

McGovern said that he decided to speak up now in an effort to unite the party.

``It's very painful for me to call an old friend like President Clinton who I've known for 36 years and tell him I no longer go with the campaign.'' McGovern said that Clinton told him that Senator Clinton plans to remain in the race at least through June 3.

In the Senate, McGovern represented South Dakota, which is holding its primary June 3.

To contact the reporter on this story: Christopher Stern in Washington at cstern3@bloomberg.net.

Last Updated: May 7, 2008 18:58 EDT