Throughout his life - ever since he resolved his high school indecision between his dream of a career in baseball or a life in law - the self-effacing Judge Alito, President Bush's new choice for the Supreme Court, has made his mark with quiet dedication rather than showy display. He has cloaked his formidable intellect in modesty, an attribute both surprising and endearing to colleagues in high-octane legal circles.

While Judge Alito, 55, has built a reputation for decency, he has also compiled a conservative record that is coming under intense scrutiny from activists on the left and the right who understand his potential for shifting the balance on the bench.

As a federal appeals court judge for 15 years, Judge Alito has amassed a more extensive paper record than either John G. Roberts Jr., who sailed through his confirmation as chief justice, or Harriet E. Miers, the White House counsel, who withdrew after withering attacks on her credentials and conservative bona fides.

Judge Alito's jurisprudence has been methodical, cautious, respectful of precedent and solidly conservative, legal scholars said. In cases involving the great issues of the day - abortion, the death penalty and the separation of church and state - Judge Alito has typically taken the conservative side.

Like Justice Scalia, Judge Alito is an Italian-American from Trenton, whose jurisprudence is indisputably conservative. But while Justice Scalia is known for his caustic writing and argumentative manner, Judge Alito is described by clerks, lawyers and former schoolmates as a man who takes extraordinary care to be gentle with others and is quick to help a struggling lawyer arguing before his court.