MILWAUKEE — Relegated to the Republican undercard debate for the first time, Chris Christie focused on attacking Democratic front-runner Hillary Rodham Clinton as he tried to use his performance as a springboard back into the field’s top tier.

“Hillary Clinton’s coming for your wallet, everybody. Don’t worry about Huckabee or Jindal, worry about her,” he said early on in the hourlong debate. “If you think Mike Huckabee won’t be the kind of president who will cut back spending, or Chris Christie, or John Kasich, wait till you see what Hillary Clinton will do to this country,” he added. “She will drown us in debt. She is the real adversary tonight.”

The approach couldn’t have been more different from that of an aggressive Bobby Jindal. The Louisiana governor repeatedly jabbed at Christie and his fellow Republicans, criticizing their states’ economic records and accusing them of being watered-down Democrats instead of true conservatives.

“Let’s not just beat Hillary,” Jindal said. “Let’s elect a conservative to the White House, not just any Republican.”

It was a crucial moment for the two sitting governors, each trying to remain relevant in a race for the Republican presidential nomination that has favored political novices who have never held public office. They appeared with former Pennsylvania Sen. Rick Santorum and former Arkansas Gov. Huckabee, who was also relegated from the prime-time debate to the earlier event.