Rick Santorum pushed back Monday against Mitt Romney’s constant needling of the former Pennsylvania senator’s “take one for the team” comment during last week’s Republican presidential debate in Arizona, dubbing Mr. Romney the “most liberal guy” in the GOP race.

Mr. Santorum said during the debate that a number of votes he cast in Congress reflected his loyalty to the party rather than his personal preferences. Mr. Romney, locked in a tight battle with Mr. Santorum in the Arizona and Michigan primaries Tuesday, repeatedly has criticized Mr. Santorum’s defense as a failure of leadership.

“I’ll tell you what team I was on. I was on George Bush and the Republican conservatives’ team, and I have a voting record that backs it up — a 90 percent conservative voting record,” Mr. Santorum said Monday in an interview with The Washington Times-affiliated “America’s Morning News”...