How concerned is Mitt Romney about Newt Gingrich’s ascent in the polls?

If the Romney camp’s conference calls slamming the former House speaker are any guide, the former Massachusetts governor is doing all he can to tamp down on Gingrich’s newfound momentum.

Former House speaker Newt Gingrich (R-Ga.). (Jason Reed/Reuters)

“Last night, the debate showed a clear difference in leadership,” Mack told reporters. “I think it’s clear to everyone – but apparently we need to do a conference call – that Newt Gingrich failed the test of leadership when he lost control of his Republican majority. They found him to be divisive and erratic. Clearly, Newt engaged in activities that were unethical and wrong – so severe, in fact, that he was censured and fined by his own Republican majority, $300,000.”

He added:

“We’re not looking for a game-show host for president of the United States. That’s frankly scary to think that. We’re looking for a president who can lead.”

Camp defended Romney as “a proven leader” and focused most of his criticism on President Obama, who he said has “failed to lead on the tax reform issue.”

The call comes ahead of Obama’s third State of the Union address, which he will deliver before a joint session of Congress on Tuesday night.

It also comes as Romney has released his tax returns, responding to pressure from Gingrich and others. Romney had previously said he would release the returns in April.

Asked about the fact that the returns show Romney pays a rate of about 14 percent in taxes, Mack responded that “Mitt Romney is an American success story, and this is something that we should celebrate in America.”

Camp – who heads the House’s powerful tax-writing committee and was a member of last year’s “supercommittee” talks on debt-reduction – responded by arguing that “even CNN has reported that 85 percent of Americans have an effective tax rate of less than 15 percent.”

“So, what someone’s top marginal rate is is not exactly what they actually pay,” he said. “As we know, at the lower half of the economic scale, half of Americans pay no income taxes at all, mostly due to credits and deductions, and their effective tax rates are zero. In many cases they actually get dollars back from the government. Look, I think he’s disclosed. He’s put this out there. I think what’s more important is that his effective rate is probably higher than most people’s, and the effective tax rate’s always going to be lower than what someone’s top income tax rate is.”

The lawmakers also took aim at Gingrich’s release of his contract with Freddie Mac, the mortgage giant that paid the former House speaker $25,000 a month in consulting fees. Gingrich has defended his work at the mortgage lender, arguing that he was a “historian” and not a lobbyist.

Mack said that Gingrich needs to reveal more details of his work, contending that the information released “doesn’t pass the smell test.”

“First of all, it’s only one year. ... It’s very vague. It doesn’t give any details,” he said. “A lot of the exhibits that were supposed to be included weren’t.

“Clearly, from most perspectives, it looks like they’re hiding something,” he added.

A Gingrich spokesman did not immediately respond to a request for comment.