DES MOINES, Iowa — Republican presidential hopefuls called for cuts in taxes and government regulations in campaign debate Saturday night, agreeing they must attack unemployment and revitalize an anemic economy that is the overwhelming issue in the 2012 race for the White House.

Alone among the six contenders on stage, former Massachusetts Gov. Mitt Romney ventured a prediction about job creation, saying his plan would translate into 11.5 million jobs in four years.

Former House Speaker Newt Gingrich said he favors an elimination of the estate tax, a reduction in the corporate tax to 12.5 percent and a provision that allows businesses to write off the cost of new equipment in the year they purchase it. "Those steps would dramatically begin to create jobs," he said.

The debate was the first since Herman Cain suspended his campaign and Gingrich shot to the top of the public opinion polls nationally and in Iowa, where precincts caucuses on Jan. 3 begin the long process of selecting delegates to the Republican National Convention next summer.

Romney runs second in the polls, a now-and-again front-runner who has thus far been unable to attract enough conservative support to dispatch his rivals.

Gingrich's opponents made it clear they're aware he has leapfrogged Romney to become the GOP front-runner less than a month before the leadoff Iowa vote to determine Obama's challenger.

Romney, the earlier leader in national polls, has responded with an aggressive attack on the former House speaker, trying to raise questions about Gingrich's leadership, judgment and party loyalty.

Gingrich stirred up trouble for himself right before the debate, intended to focus on the federal budget deficit, when he told a Jewish cable channel that Palestinians are an "invented" people and are really Arabs who chose not to live elsewhere.

His campaign clarified the comments, released Friday, by saying that Gingrich supports a negotiated peace between Israelis and Palestinians. "However, to understand what is being proposed and negotiated you have to understand decades of complex history, which is exactly what Gingrich was referencing," according to a statement Saturday.

But Gingrich maintained a cool tone toward the Palestinians during a forum on national security prior to the debate.

"If we had a country next to us firing missiles, how eager would we be to sit down and negotiate?" Gingrich said at the forum.

The fast-developing Gingrich-Romney rivalry threatened to overshadow the four other candidates scheduled to attend the debate at Drake University: Reps. Michele Bachmann of Minnesota and Ron Paul of Texas, along with Texas Gov. Rick Perry and former Pennsylvania Sen. Rick Santorum.

It was the 12th debate of the Republican nominating campaign, the first since businessman Herman Cain suspended his campaign a week ago, and the 11th that both Romney and Gingrich attended.

Gingrich has emerged as the leader in Iowa and some other early-voting states after his campaign nearly disintegrated last summer. Paul and Romney are next in Iowa polls.

The policy-minded former college professor, has used the steady stream of nationally televised debates to gain momentum while challengers of the moment to Romney's establishment campaign have risen then fallen throughout the summer and fall.

For most of the week, Romney assigned surrogates to highlight Gingrich's criticism of important parts in the House budget blueprint. Romney weighed in himself Friday, noting Gingrich's support for ideas such as mining the moon.

Romney suggested Gingrich's background as a Washington insider would be a liability, a theme Gingrich might expect at the debate and in the weeks ahead of the Jan. 3 caucuses in Iowa.

"We're very different people, my background and his. We followed very different paths," Romney told The Des Moines Register editorial board. "And someone who has spent their time in the private sector has by far the best chance of defeating the president."

Bachmann has called Gingrich an "influence peddler." Santorum has criticized Gingrich's record in Congress. Perry has hit his support for a national insurance mandate in the 1990s. Paul is running an ad accusing Gingrich of "serial hypocrisy."

Romney supporters have begun describing Gingrich as self-serving and untrustworthy, assessments Romney said he stood by during the Register interview. They said Gingrich has a tendency for off-the-cuff remarks aimed at promoting his own policy acumen or stirring controversy, and that Romney's disciplined message would help keep the focus on Obama's handling of the economy.

Romney's strategy with Gingrich is beginning to mirror what his campaign did with Perry, who entered the race in August and immediately rose to the top of polls.

Ahead of debates, Romney's team rolled out new attacks on Perry, first on some of the governor's comments on Social Security and then on his immigration record. Romney also delivered those attacks himself in two debates.

Romney has turned in a series of strong debate performances. He's made few mistakes and hasn't been repeatedly attacked by his rivals.

But it's Gingrich's performances that voters have noticed.

In a Des Moines Register poll released in early December, 50 percent of likely caucus-goers said Gingrich is the best debater. Romney was a distant second with 14 percent.