SCOTTSDALE, Arizona (Reuters) - Presumptive Republican presidential nominee Mitt Romney worked on Friday to rally party leaders behind his cause and overcome lingering suspicions that he is too moderate, but failed to get all to pledge allegiance.
Romney called for unity at a Republican National Committee conference in the Arizona desert that brought together party representatives from each state, some of whom had backed one of Romney's rivals for the nomination.
In his speech, Romney kept the focus on Democratic President Barack Obama's handling of the sluggish U.S. economy. He recognized his vanquished Republican rivals, from Michele Bachmann to Rick Santorum, mentioning them all by name and thanking them for having the courage to run.
"Each one of them is going to play a vital role in making sure we win in November," said Romney. The former Massachusetts governor needs as much support as he can get from fellow Republicans in what is expected to be a tough fight with Obama as the November 6 election approaches.
Romney lagged Obama by 6 percentage points in a new NBC/Wall Street Journal survey, although a few other polls have shown him ahead.
Some Republican committee members declined to fall in line with Romney's attempts to bring the party together under his candidacy after months of bruising primary fights.
In a private reception before his luncheon speech, Republican delegates were asked to sign a pledge to support Romney and about 100 did so, a campaign official said.
But Iowa's three conservative representatives did not sign the pledge and CNN said there was a heated exchange in the hallway outside the reception.
Some party representatives had been hoping one of Romney's rivals would become the standard bearer. Iowa, for example, narrowly voted for Santorum over Romney in its January nominating contest.
Reinforcing the idea that Romney, who is trying to dispel criticism that he is too stiff, has a "likeability gap" with voters, a recent Washington Post/ABC News poll offered a glaring picture: 56 percent said they had a favorable opinion of Obama while only 35 percent said the same of Romney.
The NBC/Wall Street Journal poll also showed that the president is seen as more likeable and someone who cares more than Romney, a former business executive, about average people. Romney had 43 percent to Obama's 49 percent in a match-up.
But in a key area - ideas to improve the U.S. economy - Romney led Obama by 40-34 percent.
In his second presidential bid, Romney is playing well to the Republican establishment. More state chairmen are now getting behind him after the departure from the race last week of Santorum, a former U.S. senator from Pennsylvania who was his main rival.
"My sense is that when the primary process started, a lot of state chairs liked a lot of the different candidates, but now that Romney is almost the presumptive nominee, they're all coming on board," said Steve Duprey, a party leader in New Hampshire. "He's proven himself after a long, rugged battle and I think people are starting to get enthusiastic."
The Republican presidential nominee from 2008, Senator John McCain of Arizona, conducted a symbolic passing of the torch to Romney at Friday's event.
"I am so gratified to see our party coming together on a solid team that is going to elect him president of the United States," McCain said at the lunch.
Duprey said Romney should use his wife, Ann, as often as possible on the campaign trail to lighten up his image.
"The more time he spends out on the campaign trail with Ann Romney, who is his best surrogate, and the more time he spends in smaller, more intimate events ... the more people will see he's a competent and genuine person," Duprey said.
Romney also moved to try to improve his standing among Hispanic voters, staging a roundtable to discuss issues important to them. Hispanics could be a key voting bloc in Southwestern states like Arizona, New Mexico and Nevada.
Romney sat down in Tempe with a group of Hispanic business, education and local officials picked by the local Republican Party. He invited them to raise anything they wanted from economic conditions to illegal immigration, a big issue in Arizona.
Tony Rivero, a city councilman in Peoria, Arizona, called for a comprehensive overhaul of U.S. immigration laws. Democrats and Republicans in Washington have been stalemated for years over what to do about the estimated 11 million illegal immigrants in the United States.
"We have a broken system," Rivero said. "I think we have to look at the issue and solve it completely."
Manuel Pacheco, former president of the University of Arizona, told Romney he likes the concept behind the proposed "Dream Act," which would offer a path to citizenship for young immigrants through military service and college education, but recognizes that it is politically "toxic" at the moment. He called on Romney to offer a "glimmer of hope" on the topic.
Romney did not comment on the immigration problem at the event or at a subsequent campaign rally.
But he told Fox News he would like the United States to move ahead with immigration reform legislation and find a "realistic way" for more legal immigration.
"I'd like people who have skill and experience and who speak English, education, I'd like to make it easier for them to come to the country," he said.
Republicans believe they can draw Hispanic voters from Obama by pressing Romney's economic message, including the case that the growing minority group has as big a need for jobs as anyone else.
RNC Chairman Reince Priebus said the main issue for Hispanics was jobs, not immigration, which he said in any event Obama has failed to address in three years as president.
"He didn't deliver a darned thing on immigration reform," Priebus told Reuters.
Editing by Alistair Bell and Christopher Wilson