In a comment that drew much criticism Friday, Senator Hillary Clinton invoked a tragic 1960s assassination as a reason for why she is staying in the race for the Democratic nomination.

"My husband did not wrap up the nomination in 1992 until he won the California primary somewhere in the middle of June, right? We all remember Bobby Kennedy was assassinated in June in California. I don't understand it," said Clinton.

Barack Obama's campaign said Clinton went too far, declaring the comment made to a South Dakota newspaper editorial board was “unfortunate and has no place in this campaign."

Clinton quickly back-tracked from her comments about Robert F. Kennedy's assassination in June 1968.

"I regret that if my referencing that moment of trauma for our entire nation and in particular the Kennedy family was in any way offensive. I certainly had no intention of that whatsoever," said Clinton.

She said she was showing how past primary contests went into June, and that the Kennedy family was on her mind due to Senator Edward Kennedy's battle with brain cancer.

All three presidential candidates have a busy weekend lined up, as the race for the White House heads into the summer, but Democratic presidential hopeful Hillary Clinton got some unexpected criticism from one of her supporters.

Clinton campaigned in South Dakota Friday, the site of one of the three remaining Democratic primaries. She was in Florida Thursday, pushing for the state's delegates to be seated at the Democratic convention.

Governor David Paterson, a superdelegate and Democratic National Committee member who has publicly campaigned for Clinton, said Thursday she's showing a little "desperation." He called on her to give up efforts to count votes from Florida and Michigan.

Illinois Senator Barack Obama campaigned in Florida Friday.

He will be in Connecticut Sunday to deliver the commencement address at Wesleyan University, in place of Massachusetts Senator Edward Kennedy. Kennedy pulled out yesterday in light of his recent cancer diagnosis. The Massachusetts lawmaker endorsed Obama in his race against Clinton.

Meanwhile, John McCain rejected the endorsement of televangelist John Hagee, after an audio tape surfaced in which the Texas preacher said God sent Adolf Hitler to help Jews reach the Promised Land. McCain called Hagee's remarks "indefensible."

The presumptive Republican nominee is hosting three possible vice-presidential candidates at a party this weekend at his Arizona home. Florida Governor Charlie Crist, Louisiana Governor Bobby Jindal and former Massachusetts Governor Mitt Romney are expected to be there.

Meanwhile, speaking on his weekly radio show Friday, Mayor Michael Bloomberg skirted questions about his interest in the job of vice-president.

"I have a job which I said I've had about 587 days left, but who's counting? And I will continue in that job," said Bloomberg. "I just hope that this country has great alternatives. You need two good presidential candidates for the general election and also you want to make sure that whoever the two candidates pick, those people could be presidents of the United States."

Bloomberg said he did not discuss the matter during a recent meeting with McCain.

Bloomberg squashed speculation that he would run for President in February, ending more than two years of rumors that he would do so.