NEW YORK - For all her talents, Sen. Hillary Rodham Clinton does not seem to be able to match her husband's track record of near-perfect political pitch, as many have observed.

Whatever the cause, Clinton's reference Friday to the June 1968 assassination of Robert F. Kennedy as she attempted to explain her reasons for remaining in the race struck some who heard it as a veiled reference to her Democratic primary rival, Sen. Barack Obama.

Plenty of voters, black and white, worry that Obama faces extra risks to his safety as the first black candidate to have a realistic possibility of being elected president. Even the vaguest suggestion that threats to Obama's safety are a reason for Clinton to continue her candidacy against overwhelming odds was bound to rile the New York senator's critics.

Certainly that's the way Obama's campaign initially appeared to interpret her remark to a South Dakota newspaper, the Argus Leader in Sioux Falls.

"Sen. Clinton's statement before the Argus Leader editorial board was unfortunate and has no place in this campaign," Obama campaign spokesman Bill Burton said in a statement Friday.

Yesterday while campaigning in Puerto Rico, Obama seemed inclined to excuse Clinton's remark as a simple misstep.

"I have learned that when you are campaigning for as many months as Sen. Clinton and I have been campaigning, sometimes you get careless in terms of the statements that you make - and I think that is what happened here. Sen. Clinton says that she did not intend any offense by it, and I will take her at her word on that," Obama told Radio Isla Puerto Rico.

Except for Clinton, Obama was the first presidential candidate to receive Secret Service protection in the 2008 race. That happened in May 2007, which was the earliest such security measures had ever been taken for a candidate. Clinton has had continued Secret Service protection since she left the White House.

In her interview with the newspaper, Clinton mentioned the assassination when asked why some were calling for her to end her campaign in the face of ever-dwindling odds.

The woman who holds the U.S. Senate seat for New York once held by Kennedy said she didn't understand why, given the history of primaries, some Democrats were calling for her to quit.

"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. You know, I just, I don't understand it."

After the fury unleashed by her remark, Clinton said she regretted any offense she might have caused.

The Rev. Al Sharpton, a New York-based civil-rights activist and former presidential candidate, said he spoke to Clinton yesterday morning and was convinced that she meant no harm. But, he added, "We have not gotten to the point where we can talk about these assassinations like they don't mean anything today."