May 25 (Bloomberg) -- Hillary Clinton, criticized for a reference to the 1968 assassination of Robert F. Kennedy, said in a New York Daily News commentary she is still campaigning for the Democratic Party's presidential nomination because she believes she is the strongest candidate.

``I am running because I believe I'm the strongest candidate to stand toe-to-toe with Sen. McCain,'' the New York senator wrote in the op-ed piece. Senator John McCain of Arizona has wrapped up the Republican nomination.

``Delegate math might be complicated, but electoral math is not,'' she wrote. The campaign of her rival for the nomination, Senator Barack Obama of Illinois, said May 22 that he is only 56 delegates short of the 2,026 needed to secure the nomination. Clinton said she has won in the crucial swing states needed to win the general election, such as Florida, New Jersey, Ohio and Pennsylvania.

Clinton wrote that she can still win on the merits, and because ``my parents did not raise me to be a quitter.'' She said that, while ``pundits and politicians'' have called on her to end her candidacy, recent victories in West Virginia and Kentucky show that Clinton is still winning votes from people despite being told the ``race is over.''

``I am running because I believe staying in this race will help unite the Democratic Party,'' Clinton wrote. ``I believe that if Sen. Obama and I both make our case, and all Democrats have the chance to make their voices heard, in the end everyone will be more likely to rally around the nominee.''

The former first lady also repeated that her reference two days ago to Kennedy's assassination in June 1968 was only to make the point that ``the length of this year's primary contest is nothing unusual'' because both Kennedy's and her husband's primary campaigns continued into June, she said.

To contact the reporter on this story: Dan Hart in Washington at dahart@bloomberg.net.

Last Updated: May 25, 2008 09:43 EDT