WASHINGTON - The White House dispatched Michelle Obama to defend Supreme Court nominee Sonia Sotomayor yesterday, part of a broad offensive that came as former GOP House Speaker Newt Gingrich backed off his harsh criticism of her as a racist.

Sotomayor, who grew up in a New York City housing project and went on to Princeton and Yale universities, "says she still looks over her shoulder and wonders if she measures up," the first lady said at Howard University.

It was a subtle counter to Republicans who have cited Sotomayor's speeches and writings about how her background affects her work as a judge to question whether she would let her personal biases interfere with her judicial decisions.

Hours earlier, Gingrich told supporters in a letter that he shouldn't have called Sotomayor a racist, adding that the word had been "perhaps too strong and direct."

But he said that the 2001 speech that prompted his remark, in which Sotomayor said she hoped the rulings of a "wise Latina" would be better than those of a white male without similar experiences, was still unacceptable. *