WASHINGTON — Onetime Republican front runner Mitt Romney sought to blunt the surging momentum of his main rival Newt Gingrich on Wednesday by insisting he is just too "zany" to be president.

"Zany is great in a campaign. It's great on talk radio. It's great in print, it makes for fun reading," Romney told The New York Times in an interview.

"But in terms of a president, we need a leader. And a leader needs to be someone who can bring Americans together," he added, suggesting that Gingrich did not have the temperament or economic experience to lead.

"I actually think you need someone who actually understands the economy leading the country," he said.

"Zany is not what we need in a president."

The comments were Romney's latest attacks on Gingrich as the first voting nears, on January 3 in the Iowa caucuses, in the Republican Party nominating contest to decide who will take on President Barack Obama in next November's election.

Gingrich has rocketed to the top of Republican presidential polls in recent weeks, faring well in several televised debates and touting his fiscal conservative credentials.

In surging past Romney -- the latest Wall Street Journal poll has Gingrich leading Romney 40 percent to 23 percent nationally, although Romney fares better than Gingrich when running head-to-head against Obama -- Gingrich has vowed not to go negative in his campaign.

"I'm happy to tell you about my approach and commitment to being positive and focuses on new solutions and ideas," Gingrich said on Wednesday in Iowa.

That positivity has been put to the test with Romney sharpening his attacks on the former House of Representatives speaker.

Romney last week unveiled an ad emphasizing his family values, a clear dig at Gingrich who is under fire from members of the party's religious base over his admitted extramarital affairs and two divorces.

And over the weekend, Romney said he thought Gingrich ought to return the reported $1.6 million he earned as a consultant to housing giant Freddie Mac.

Gingrich took the bait, retorting this week that "if governor Romney would like to give back all the money he's earned from bankrupting companies and laying off employees over his years at Bain ... I would be glad to then listen to him."

Photo credit: Tom LeGro of NewsHour