Chris Christie was supposed to be one of Mitt Romney‘s most aggressive surrogates, constantly attacking President Obama in the waning days of the presidential campaign.

Instead, Mr. Christie on Tuesday repeatedly heaped praise on Mr. Obama for his leadership of the federal government’s response to the storm that slammed into his state on Monday.

Eight days ago, Mr. Christie described Mr. Obama as “blindly walking around the White House looking for a clue.” On Tuesday morning, he was effusive about Mr. Obama’s administration, calling the storm response “wonderful,” “excellent” and “outstanding.”

The overnight transformation of Mr. Christie from political slasher to disaster governor is a reflection of the magnitude of the devastation in New Jersey. Asked on Fox News whether Mr. Romney might tour damage of the state, Mr. Christie was dismissive.

“I have no idea, nor am I the least bit concerned or interested. I have a job to do in New Jersey that is much bigger than presidential politics,” Mr. Christie said. “If you think right now I give a damn about presidential politics, then you don’t know me.”

But some Republicans have already begun grumbling about Mr. Christie’s over-the-top praise of the president at such a crucial time in the election. One Republican in Washington said Mr. Christie could have simply expressed appreciation for what any president would have done. Another Republican strategist observed that Mr. Christie’s kind words for the president were delivered with the kind of gusto that he often uses to criticize Mr. Obama.

A spokeswoman for Mr. Christie, who was scheduled to tour damage along the New Jersey coast, declined to comment about presidential politics.

Aides to Mr. Romney declined to criticize Mr. Christie, saying that they recognized the need for the governor to focus on the efforts to rescue his residents and begin recovering from the storm. Kevin Madden, a spokesman for Mr. Romney, noted that Mr. Christie said “this isn’t a time for politics.”

And yet the presidential campaign marches forward in spite of the storm. And it looks as if Mr. Romney’s campaign may have to do without Mr. Christie’s powerful voice in the homestretch.

At a rally in Richmond, Va., last week, Mr. Christie lashed out at the president in a way that few of Mr. Romney’s surrogates can. He seized on Mr. Obama’s previous comment about not being able to effect change from inside the White House and offered to buy him an airplane ticket back to Chicago.

He said the president had never learned how to lead anything, having served as a community organizer, state legislator and one-term senator.

“He’s like a man wandering around a dark room, hands up against the wall, clutching for the light switch of leadership, and he just can’t find it,” Mr. Christie said at the rally.

That probably would have been the message that Mr. Christie delivered repeatedly during the final days of the presidential campaign. But the storm’s arrival — and the damage it inflicted for Mr. Christie’s constituents — have changed that dynamic.

In several appearances on morning news programs on Tuesday, Mr. Christie went out of his way to thank the president personally, in addition to praising the operation of the federal government and its response teams.

“It’s been very good working with the president,” Mr. Christie said on the “Morning Joe” program on MSNBC. “He and his administration have been coordinating with us. It’s been wonderful.”

Speaking about the damage to his state on the “Today” show on NBC, Mr. Christie called the president “outstanding” and said the response from the Federal Emergency Management Agency had been “excellent.”

In a Twitter message from his official account, Mr. Christie said he wanted to “thank the president personally for all his assistance as we recover from the storm.”

Mr. Romney’s campaign said on Monday that Mr. Romney had talked with Mr. Christie and Gov. Bob McDonnell of Virginia as the storm approached over the weekend. Mr. Christie did not mention on Tuesday his conversations with Mr. Romney.