But her hour-long testimony made clear that Republicans are laying the ground for possible opposition to her nomination. They questioned Halligan, a longtime New York appellate lawyer, about statements she’s made or signed on to, and they renewed a long-running debate about whether the influential D.C. Circuit has more judges than it needs.

If confirmed, Halligan, 44, would quickly be on the short list for the next Democratic nominee for the U.S. Supreme Court. Four sitting justices are alumni of the D.C. Circuit, and she is President Barack Obama’s first nominee for the D.C. Circuit.