The question was one she had heard before, but this time it was asked in downright hostile terms.

“Has your mother shown any remorse for the fact that her vote cost Iraqis a million of their lives?” a student asked Chelsea Clinton on Monday at the University of Wisconsin-Madison.

Ms. Clinton replied: “She cast a vote based on the best available evidence. Perhaps you had clairvoyance then, and that’s extraordinary.”

As Senator Hillary Rodham Clinton’s presidential campaign tries to win some younger voters, her daughter is parachuting into the heart of enemy-occupied territory: college campuses in the grip of Obama fever, both in must-win and lost-cause states for her mother’s candidacy. On Saturday and Sunday, Ms. Clinton will campaign in Hawaii, the childhood home of Senator Barack Obama.

For nearly the first year of her mother’s presidential bid, Ms. Clinton, 27, was practically invisible to voters. Just before the Iowa caucuses on Jan. 3, she began appearing in the tableau of flags and signs behind her mother at speeches. But when it became clear that Mr. Obama was making off with many people her age, Ms. Clinton decided to speak out. Unlike most other family members who hit the campaign trail, she does not offer an intimate portrait of the candidate, and she recounts old family stories only when her audiences clamor for one. (Memory lane can be a dangerous place: waxing about White House Christmases might remind voters of just how many her family has already had.)