ATLANTIC, Iowa (AP) — For Mitt Romney, it's another day, another rival.
On Sunday, he slapped at the surging Rick Santorum.
"Our backgrounds are quite different," Romney told reporters, who were crowded into a back room at the Family Table Restaurant. "Like Speaker Gingrich, Senator Santorum has spent his career in the government in Washington. Nothing wrong with that. But it's a very different background than I have."
He then called Santorum a good guy who has worked hard and probably will do well in Tuesday's caucuses. The mild criticism was an attempt to stoke doubts about his latest opponent without angering — or alienating — his supporters.
Like other recent comments about his rivals, Romney had to be asked to engage. His comments came in response to a question about how he would persuade voters to back him over the former Pennsylvania senator.
A lot can change in just a few days here. The race to win the approval of Iowa Republicans is as unsettled as ever in a contest that has seen every contender at the front of the pack at one point or another.
That so many have held the frontrunner title says a lot about the lack of enthusiasm for Romney. He's been running for president for the better part of five years, but he still doesn't excite the GOP base.
Late last week, Romney had to field questions about an ascendant Ron Paul. Before that, it was the rising Newt Gingrich. A few months ago, Rick Perry.
And through it all, Romney has delivered the same optimistic campaign speech that all but ignores his GOP rivals. Instead, Romney praises America and attacks President Barack Obama before large crowds.
"I don't think I've spent a lot of time trying to describe differences on policy and detail on myself and the other candidates, but instead I focus on the things I believe," Romney said Sunday.
Romney has been much sharper with the rivals when his campaign worried they could have the money, organization and potential support to challenge him for the Republican presidential nomination.
He didn't hesitate to go after Gingrich, when the former House speaker was at the head of the pack in polls. While Romney has stayed positive in TV ads, his allies are airing anti-Gingrich ads in Iowa and early primary states, including South Carolina and Florida. And Romney's campaign, itself, has attacked Gingrich in direct mail pieces.
Just last week, Romney compared Gingrich's failure to earn a spot on Virginia's primary ballot to a 1950s sitcom.
"It's more like Lucille Ball at the chocolate factory," he said when a reporter asked him about Gingrich's troubles.
In the face of the attacks, Gingrich has fallen back in early-state and national polls. Speaking to reporters in Iowa Sunday, Gingrich complained that his campaign had been "Romney-boated," referring to the third-party group Swift Boat Veterans for Truth that helped sink Democrat John Kerry's presidential candidacy in 2004.
Romney hasn't been as sharp-tongued about other opponents.
As with Santorum, the criticism of Paul was made almost off-handedly.
Asked about the libertarian-leaning Paul's spike in polls last week, Romney said, "I don't think Ron Paul represents the mainstream." He added, "I'm working harder than anyone to make sure he's not the nominee."
As his opponents fight with each other, Romney has sought to stay above the fray.
He's made a handful of campaign stops every day since last Tuesday, with a break on New Year's Eve to spend some time campaigning in New Hampshire. He plans to spend caucus night in Iowa before returning Wednesday morning to New Hampshire, which holds the nation's first primary.
At his stop in Atlantic, scores of reporters, photographers and camera crews packed into a small restaurant, making it impossible to tell how many Iowa voters were seated at the tables and waiting to see Romney. His staff ended up bringing him into the event through the kitchen because he wasn't able to get through the front doors.
The voters who did make it inside weren't all pleased.
"It's awful in here," said Cathy Dowhey, 51, who plans to speak on behalf of Romney at her caucus in Atlantic. She braved the crush to get Romney's signature on the package of information the campaign mailed to her so she could prepare for the role.
Some didn't make into the restaurant.
Don McLean, a local pastor who is leaning toward backing Santorum, looked sideways at his 14-year-old daughter as he waited outside in freezing temperatures.
"It's too crowded," McLean said as he stood a few feet from the front door.
He waited a few more minutes. With still no sign of Romney's arrival, he got into his car and drove away.
"We're going home to watch some football," he said.