Mitt Romney made a fresh appeal Sunday to middle-class moms who are frustrated by rising gas prices, hoping female voters can help speed up his slog to the Republican presidential nomination and rehabilitate his standing with independent voters.

Opening a two-day campaign swing across Illinois heading into Tuesday’s critical primary, Romney and his wife, Ann, made a populist play for the support of women, a demographic his strategists see as key to beating rival Rick Santorum in Illinois and in the primaries to come.

Romney increased his lead in the delegate count with a commanding victory in Puerto Rico, which held its primary Sunday. Early returns showed him winning about 80 percent of the vote and he was projected to claim all 20 delegates in the U.S. territory, where both he and Santorum campaigned hard in recent days.

Reveling in the night’s results and looking ahead to a strong showing in Illinois, Ann Romney effectively called for an end to the nominating contest.

“We need to send a message that it’s time to coalesce, it’s time to come together, it’s time for us to get behind one candidate and get the job done so that we can move on to the next job, which is bringing us one step closer to defeating Barack Obama,” she said, standing alongside her husband at a Sunday evening town hall meeting in Vernon Hills.

But Santorum, who spent Sunday in Louisiana, which will hold its primary Saturday, cast his insurgent candidacy in religious terms and said he should not be dismissed easily.

“One of the great blessings I’ve had in every political campaign is people underestimate me, people underestimate what God can do,” Santorum said at a Louisiana church, according to the Associated Press.

But the focus of the race was on Illinois, where both men will be campaigning Monday. This latest battleground in the Romney-Santorum rivalry will hold an open primary Tuesday that will award 54 bound delegates proportionally and provide a jolt of momentum to the victor.

Romney is hoping a pocketbook pitch will pull female voters toward him and increase his lead over the former senator from Pennsylvania. At each stop Sunday, Romney repeated his call on Obama to fire the “gas-hike trio” — Energy Secretary Steven Chu, Interior Secretary Ken Salazar and Environmental Protection Agency Administrator Lisa P. Jackson.

“You’ve got moms that are driving their kids to school and practice after school and other appointments and wonder how they can afford putting gasoline in the car, at the same time putting food on the table night after night,” Romney told supporters at a pancake breakfast in Moline, Ill.

“This president doesn’t understand the economy. It’s time to put in place an economic heavyweight, and I am, and I’ll get that job done,” added Romney, who worked 25 years as a businessman before launching his political career.

Obama campaign adviser David Axelrod responded to Romney’s attacks in an interview on CBS’s “Face the Nation” in which he criticized the former Massachusetts governor’s record.

“If he thinks he’s an economic heavyweight, he must be looking in a funhouse mirror, because that is not the record of an economic heavyweight,” Axelrod said.

Ann Romney, who campaigned alongside her husband Sunday, was more direct in her plea to women.

“I love it that women are upset, too,” she said of Obama’s record. “Women are talking about the economy. I love that. Women are talking about jobs. Women are talking about deficit spending. Thank you, women. We need you. We all need you in November, too. We have to remember why we’re upset and what we’ve got to do to fix things.”

The economy has been the bedrock issue of Romney’s campaign, but he has rarely spoken of it in such populist terms. At campaign stops Sunday, he recalled recently meeting a landscaper in St. Louis whose team can hardly afford to gas up their trucks to get to sites.

And Romney talked about a woman he met who is out of work and told him she has had to turn down temporary teaching jobs.

“When she considers the cost of gasoline to get to the job and back, it doesn’t make sense to go off unemployment” benefits, he said.

Romney is trying to regain the momentum he lost with third-place finishes last week in Alabama and Mississippi.

AP reported that Santorum said of his opponent Sunday: “This is a primary process where somebody had a huge advantage, huge money advantage, huge advantage of establishment support, and he hasn’t been able to close the deal and even come close to closing the deal. That tells you that there’s a real flaw there.”

Polls show Romney leading in Illinois, but to win big he needs to run up big margins in the Chicago suburbs and limit Santorum’s strength in the more conservative downstate region. There were some signs his economic message was resonating.

“I drive to my children’s school three times a day,” said Heidi Carlson, 40, a stay-at-home mom who saw the Romneys speak at a farmer-themed restaurant in Rockford.

“We’re spending a lot for gas. I connect completely to what he says.”

Exit polls have shown Romney consistently outperformed his Republican rivals among women in many primaries so far. A Washington Post-ABC poll last week found that among women who are Republican or GOP-leaning independents, Romney edges Santorum 35 percent to 30 percent, with former House speaker Newt Gingrich at 10 percent.

But among all women, including Democrats, Obama leads Romney by 50 percent to 42 percent, according to the poll.

Romney advisers believe Santorum’s hard-edged conservatism makes him vulnerable with female voters — particularly in the populous Chicago suburbs, where female Republicans tend to be fiscally conservative but more socially moderate.

“Santorum’s always had a problem with women and these economic issues always resonate with women,” said Romney chief strategist Stuart Stevens. But he cautioned that Romney’s focus Sunday does not represent “a sudden deep dive.”

Romney again trumpeted his economic credentials as he continued the main line of attack he has used for months against Santorum as well as Gingrich, who was off the campaign trail Sunday.

“They spent their life in Washington,” Romney said in Rockford. “Nothing wrong with that. Washington’s a great place. [It’s] just got too many politicians. You see, the problem is they go there and stay there. . . . My view is they ought to go, serve and then go home and get a job again and understand how the economy works.”

Romney said he believes his business experience gives him “the best chance — and perhaps the only chance — of actually replacing Barack Obama as president of the United States. . . . I don’t think you are going to replace an economic lightweight with another economic lightweight.”

Polling manager Peyton M. Craighill contributed to this report.