Republican presidential candidate, former Massachusetts governor Mitt Romney speaks as he campaigns in Bedford, N.H., Dec. 20, 2011. (Elise Amendola/Associated Press)

Responding to Gingrich’s complaints about an onslaught of negative television advertisements about him that a political action committee run by Romney supporters is airing in Iowa, Romney said the former House speaker should toughen up.

“If you can’t stand the relatively modest heat in the kitchen right now, wait until Obama’s hell’s kitchen shows up,” Romney told reporters here Wednesday. “Obama’s putting together a billion dollars. He’s going to be attacking us day and night — he’s already begun attacking me.”

Romney made the remarks to reporters inside the Stage Restaurant on Keene’s town square, where he met with supporters to kick off his three-day bus tour across New Hampshire. Restore Our Future, a so-called “super PAC” financed by Romney supporters and run by former Romney political aides, has aired more than $2 million worth of television ads in Iowa, many of them attacking Gingrich. Romney has declined to tell the group to pull the negative ads, citing campaign finance laws than ban him or his campaign from coordinating with the group.

”I would love to be able to coordinate, to manage what the PAC says and to run its ads and to tell them what to do and what not to do,” Romney said. “I’m not allowed to do that, as you know.”

While he cannot legally coordinate strategy with Restore Our Future, Romney is free to help raise money for the group: The Republican candidate has appeared at multiple fundraising events for the super PAC since the summer, according to news reports. FEC rules allow candidates to solicit money on behalf of super PACs within the confines of federal contribution limits, which currently stand at $5,000 for the primary and general elections combined.

Although Gingrich has not run any negative advertisements against Romney or any other candidate, Romney pointed out that his rival has not failed to draw contrasts.

“Speaker Gingrich has had a few less than generous things to say about me over the campaign and, you know, I’m a big boy,” Romney said. “That’s the nature of a campaign, to point out distinctions with one another.”

Romney added: “It’s probably a good thing for us to get this out in the air right now so people can have the chance to know what’s going to come down the road if any one of us becomes the nominee.”

Staff writer Dan Eggen contributed to this story.

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