"If he has a conservative running mate, I'm sure that would help," said Nancy Vavricka, 67, of Cedar Rapids.
On the other side of the diner, Mike Gregoricka, 55, of Springville, said he wanted to know more about Christie's position on gun control and questioned whether he was conservative enough.
"He's got to prove to me he is," Gregoricka said.
As he went table to table at MJ's, Christie, who was on a fund-raising trip in his role as chairman of the Republican Governors Association, posed for photographs, cradled a little girl in his arms, and hugged giddy fans, who cheered when he arrived. Some urged him to run for president in 2016, a decision Christie said he hasn't yet made.
Despite the warm reception at the diner, Iowa, which holds the first presidential caucuses, could present a stiff test of Christie's ability to appeal to those in his party who view him as too moderate or pragmatic. Recent polls indicate that a sizable number of Iowa Republicans appear leery of Christie as he tries to resurrect his national profile after the Bridgegate scandal.
An NBC News/Marist Poll released last week found Christie had a higher unfavorable rating among Iowa Republicans - 33 percent - than the five other prospective Republican candidates tested.
An Iowa poll conducted in May of likely Republican caucus voters by Selzer & Co. also found Christie had higher unfavorability than other candidates - though respondents also picked Christie as having the best chance of being elected over a Democrat.
"He has some explaining to do," said J. Ann Selzer, president of the polling company. "He doesn't start with an advantage."
And in a state where religious, socially conservative voters hold considerable sway in picking a winner - former Pennsylvania Sen. Rick Santorum edged out former Massachusetts Gov. Mitt Romney to win the caucus in 2012, and former Arkansas Gov. Mike Huckabee won in 2008 - Christie could face added hurdles, experts said.
Santorum, a vocal opponent of gay marriage, "ran a very religion-oriented, God-oriented campaign," said Dennis Goldford, a professor of politics and international relations at Drake University in Des Moines. "Christie doesn't talk that language."
At a rally Thursday for Iowa Gov. Terry Branstad, Christie scattered religious references in his remarks, describing a Lutheran pastor's sermon that taught him the value of "preaching to the choir" and encouraging Republicans to go out and "sing" their message.
While religious conservatives don't form the majority of the Republican electorate in Iowa, "they're the tail that wags the dog," Goldford said. "You can't win with them alone, but you can't win without them."
A message tailored to religious voters, however, is not required to emerge from Iowa a victor, said David Oman, state cochair of Romney's presidential campaign in 2012. Romney, who became the Republican nominee in 2012, was initially declared the caucus winner, though a recount showed Santorum had won by 34 votes.
"Most candidates who come here and lay out an agenda that focuses on economic growth, liberty, and limited government do pretty well," Oman said.
Success in the caucus, he said, is not limited to coming in first: A top-three finish gives candidates momentum to compete in other early contests in New Hampshire, where Christie traveled in June and is expected to return later this month, and South Carolina.
Christie would benefit if a crowded field of candidates splits up more conservative voters, giving him a plurality of the vote, experts said.
But to win over Iowan voters used to being courted by candidates, veterans of the caucus process say Christie would have to put in the time - no small task for a sitting governor.
"This is a process that favors the unemployed," said David Yepsen, a former longtime political reporter for the Des Moines Register who is director of the Paul Simon Public Policy Institute at Southern Illinois University in Carbondale. "It's a long way from Trenton to Des Moines."
Candidates who have opted not to invest heavily in Iowa have had mixed success. Arizona Sen. John McCain avoided the state in 2008 and won the Republican nomination. But other such calculations have failed, including by former New York City Mayor Rudy Giuliani, who also largely bypassed New Hampshire during his 2008 campaign.
If Christie were to run, "he can't do what Giuliani did," said Steve Scheffler, president of the Iowa Faith and Freedom Coalition and a Republican national committeeman. "He'll have to come here and give people honest answers."
Bob Vander Plaats, president of the Family Leader, an Iowa advocacy group that opposes abortion and gay marriage, said Christie would face questions about dropping a challenge to stop gay marriages in New Jersey.
"He took a strong stance as governor on one-man, one-woman marriage, and then he backed away after the court made a decision," Vander Plaats said.
Christie was asked at MJ's whether he supported the U.S. Supreme Court's ruling in the Hobby Lobby case that said corporations controlled by religious families could refuse to provide contraceptive coverage to employees.
"I do," Christie said, in an exchange filmed and posted online by a Democratic group. On a cable news program previously, he had declined to give an opinion.
Largely absent from concerns voiced by Republicans was the national controversy over what appeared to be politically motivated traffic jams orchestrated by Christie allies last year at the George Washington Bridge. Many seemed to consider it an afterthought - "that Washington bridge thing" - and some praised Christie's response to the scandal as a sign of strong leadership.
But some uncertainty lingered. "The only thing that would even pop a red flag is that bridge thing that happened," said Tom Hommer, 65, a dispatcher for a trucking company walking in downtown Des Moines on Wednesday. "I don't have all the facts."