ROCHESTER, N.H. -- Just hours before they were set to appear on a debate stage together, Sen. Bernie Sanders (I-Vt.) took a jab at Hillary Clinton for her 2002 vote in support of the Iraq war while a senator representing New York.

“Sometimes it’s easy to apologize for a bad vote 15 or 20 years later when the tide has changed,” Sanders said at a rally here. “It is a lot harder to stand up … and cast the right vote. That’s what leadership is about, not having to apologize for standing up and fighting for what’s right.”

Sanders, a member of the U.S. House at the time, was a vocal opponent of the use of force in Iraq. Clinton, a former secretary of state, has since called her vote a mistake.

Sanders has pointed out their divergent paths on Iraq on many other occasions, but his shot on Thursday afternoon underscored the more contentious nature of the Democratic contest now that voters are starting to weigh in.

Bernie Sanders and his crowd are ecstatic with a near-tie in Iowa with Hillary Clinton on Feb. 1. (Photo by Lucian Perkins /The Washington Post)

After Clinton’s apparent razor-thin win in Iowa on Monday, two new polls on Thursday showed Sanders with sizable leads in New Hampshire.

He is leading Clinton, 61 percent to 30 percent, among likely Democratic primary voters, according to the latest CNN/WMUR poll. The margin was 58 to 38 percent in a new NBC News/Wall Street Journal/Marist poll.

Sanders has acknowledged that Clinton has more experience on foreign policy, a subject that has not been front and center in a campaign focused far more on domestic issues. But Sanders argues that his Iraq vote highlights his judgment on international affairs.