"Our founding fathers had a brilliant, really revolutionary idea that the people elected would not represent the elite, but would represent the ordinary," Huckabee, a former Arkansas governor, said at a debate in Iowa this week, a subtle poke at the former Massachusetts governor.
Thompson, a lawyer, actor and former senator from Tennessee, was more direct, saying: "My goal is to get into Mitt Romney's situation, where I don't have to worry about taxes anymore."
Romney, worth between $190 million and $250 million, took issue with that comment. But both presidential opponents already had planted the idea with Midwestern voters that Romney lives a life of wealth and privilege.
The populist pitches mark a shift for Huckabee and Thompson, two Southerners who, while starting their lives in families of modest means, now live comfortably, if not lavishly.
Both are playing the class card against Romney - essentially telling Iowans that unlike him, "I am one of you, and I will speak for you" - as polls show a competitive race just three weeks before the Jan. 3 caucuses that lead off the state-by-state GOP nominating fight.
Huckabee, a Southern Baptist preacher, has come from far behind the pack of candidates to seize the GOP lead in Iowa. Romney, the front-runner for months, is fiercely challenging him to gain ground back. Thompson trails both and is hoping to benefit from daily skirmishing between the two.
In Muscatine on Thursday, Romney dismissed the jabs from Huckabee and Thompson, saying he didn't believe voters choose their president based on "the pocket book" of a candidate.
"We've had great presidents of different economic status from the Bush family and the Reagan family and others. So I don't think an appeal to the differences in income is a successful political strategy," he told reporters.
Indeed, the class arguments may not hold much weight.
For starters, the country hasn't shied away from electing men born into wealth, such as Republican George W. Bush and Democrat John F. Kennedy. And neither Huckabee nor Thompson is struggling to make ends meet like many Americans.
Some polls suggest most people don't really resent the rich; they just want to join them.
However, two-thirds of people in a Gallup Poll in April said the distribution of money and wealth in the country is not fair, and only a third of people in a Gallup Poll in November 2006 said they'd be happier if they were rich.