Now she's really hit a nerve.

If Hillary Rodham Clinton was looking for a way to get under Rudolph W. Giuliani's skin, she may have found it today. She claimed lifelong allegiance to the New York Yankees, the Mayor's hometown team; pulled a Yankees cap over her hair, and used the power of her out-of-town address to pose with the Bronx Bombers on her own turf.

''The fact is, I've always been a Yankees fan,'' the First Lady, who was born and bred in Chicago, asserted this morning to Katie Couric on NBC's ''Today Show'' in anticipation of the championship team's visit to the White House this evening. When the puzzled Ms. Couric said she thought Mrs. Clinton was a lifelong Chicago Cubs fan, the First Lady, in a classic Clintonian gesture, quickly claimed loyalty to the Cubs, too.

''I am a Cubs fan,'' said Mrs. Clinton, who threw out the first pitch at Wrigley Field in Chicago on opening day in 1994. ''But I needed an American League team because when you're from Chicago, you cannot root for both the Cubs and the Sox. I mean, there's a dividing line that you can't cross there. So as a young girl, I became very interested and enamored of the Yankees.''

The Mayor, who has portrayed himself as the reigning No. 1 Yankees fan -- he has said he endured the wrath of his Brooklyn neighbors because he stuck up for the Yankees and not the Dodgers -- was gracious upon hearing of Mrs. Clinton's comments, of course.