IOWA CITY, Iowa (AP) — His attacks growing ever more personal, Mitt Romney on Wednesday questioned chief rival Newt Gingrich's temperament, spending habits and allegiance to both the GOP and the middle class while hecklers confronted Gingrich in the lead-off caucus state.

During a series of interviews while fundraising in New York, Romney told one media outlet that "zany is not what we need in a president" and another that Gingrich had "an extraordinary lack of understanding of how the economy works." To yet another, Romney mocked Gingrich's past accounts at a tony jeweler, saying: "He's a wealthy man - a very wealthy man. If you have a half-a-million-dollar purchase from Tiffany's, you're not a middle-class American."

Romney's campaign also rolled out an Internet video describing Gingrich as an unreliable conservative and using a clip of a climate change ad that the former House speaker filmed with House Democratic leader Nancy Pelosi.

Gingrich, in turn, sought to stay above the fray.

"They should run their campaign the way they want to and we're going to run our campaign the way we want to," Gingrich told reporters after an event at the University of Iowa.

During a speech on brain science research, Gingrich stuck to his usual campaign pitch and made no mention of Romney's charges. But the thrice-married Gingrich, who has admitted infidelity, faced criticism from his audience.

A handful of protesters drowned him out for at least three minutes, assailing Gingrich for what they called a "callous attitude toward poor people." He watched impassively from the podium in a university auditorium while the protesters shouted. But he couldn't resist responding when one person accused him of making millions of dollars on book deals and earning a "Ph.D. in cheating on your wives."

"Other than personal hostility, how would you know anything about how I publish my books?" Gingrich retorted.

The latest attacks from Romney — and the criticism from Iowans — come as the candidates prepare to square off Thursday at the final debate before the Jan. 3 caucuses and pressure increases on Romney, the one-time GOP front-runner, to curb Gingrich's rise. There's only one week for Romney to make his pitch — and tear down Gingrich — before many voters tune out over the Christmas and New Year holidays.

Much of the Iowa campaign is being waged on the air, with campaigns and their allied super PACs spending millions in TV advertisements this week alone. Meanwhile, campaigns are readying get-out-the-vote operations to ensure supporters turn out to precinct meetings on what's likely to be a frigid Midwestern winter weeknight.

Polls show most Iowans are undecided about which candidate to support or at least willing to change their minds, underscoring the volatility of the race.

For now, Gingrich, whose campaign imploded earlier this year, leads the field in Iowa surveys even as he races to build a campaign infrastructure. Romney and Texas Rep. Ron Paul trail him in surveys, while others — Texas Gov. Rick Perry, Minnesota Rep. Michele Bachmann and former Pennsylvania Sen. Rick Santorum — are working to break through with aggressive face-to-face campaign efforts.

To that end, Perry started a thousand-mile bus tour on Iowa's western edge Wednesday, telling a small group of supporters in Council Bluffs that the nation needs an outsider as president — hitting both Gingrich and Romney at the same time.

"Changing one Washington insider for another Washington insider isn't going to change a thing. Sending a Wall Streeter to Washington is not going to change a thing," said Perry, who is scheduled to campaign in Iowa daily except for a short break around Christmas as he looks for a late-game surge.

In Des Moines, Santorum expressed confidence that voters would come into his fold even though polls show him near the back of the pack.

"I'm sort of the guy at the dance, when the girls walk in they sort of walk by, and they take a few turns at the dance hall with the guys that are a little better looking, a little flashier, a little more bling," he told about 300 Nationwide Insurance employees. "But at the end of the evening, old steady Eddie's there. He's the guy you want to bring home to mom and dad."

Bachmann, too, was preparing to start her own bus tour this week, one expected to take her to all 99 counties in the state.

Rounding out their day, Bachmann, Gingrich, Perry and Santorum were scheduled to attend the screening of an anti-abortion documentary from Mike Huckabee, the former Arkansas governor who won the GOP's 2008 presidential caucuses but lost the nomination.

Romney's attacks — and his newfound willingness to talk with the media — continued to shape the race.

"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."

Earlier, Romney told Fox News that Gingrich had "an extraordinary lack of understanding of how the economy works." In an interview with CBS, Romney raised Gingrich's Tiffany's account and suggested that the former House speaker leveraged his name to earn a fortune after leaving office.

"Newt Gingrich has wealth from having worked in government," Romney said, in what is likely a preview of lines of attack for Thursday's debate in Sioux City.


Elliott reported from Council Bluffs. Associated Press writer Thomas Beaumont in Des Moines contributed to this report.

Copyright 2011 The Associated Press.