The senior Republican on the Senate Judiciary Committee says he'll vote against Supreme Court nominee Sonia Sotomayor.

Alabama Sen. Jeff Sessions says he doesn't think Sotomayor has the convictions to resist the pull of judicial activism once she becomes a justice.

His decision comes the day before the Judiciary panel is to vote on President Barack Obama's first high court nominee. Sotomayor is virtually certain to be confirmed by a vote of the full Senate by the end of next week, becoming the first Hispanic justice.

Most conservative Republicans are lining up against Sotomayor, but a handful of GOP senators are siding with majority Democrats to back her.