Hillary Rodham Clinton accused Democratic presidential rival Barack Obama of political plagiarism Thursday night and said he represented "change you can Xerox."

Obama dismissed the charge out of hand, adding in a campaign debate, "What we shouldn't be doing is tearing each other down, we should be lifting the country up."

The exchange marked an unusually pointed moment in an otherwise civil encounter in the days before March 4 primaries in Texas and Ohio — contests that even some of Clinton's supporters say she must win to sustain her campaign for the White House.

In a university auditorium in the heart of Texas, the two agreed that high-tech surveillance measures are preferable to construction of a fence to curtail illegal immigration.

They disagreed on the proper response to a change in government in Cuba in the wake of Fidel Castro's resignation. Clinton said she would refuse to sit down with incoming President Raul Castro until he implements political and economic reforms. Obama said he would meet "without preconditions," but added the U.S. agenda for such a session would include human rights in the Communist island nation.

They also sparred frequently about health care, a bedrock issue of the campaign.

HERE

Thu Feb 21, 8:55 PM ET

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Democratic presidential hopeful, Sen. Barack Obama, D-Ill., left, responds to a question as Democratic presidential hopeful, Sen. Hillary Rodham Clinton, D-N.Y., listens during the Democratic presidential debate in Austin, Texas, Thursday, Feb. 21, 2008.

(AP Photo/LM Otero)