GREEN BAY, Wisconsin., (Reuters) - As Mitt Romney sought to land a knockout blow against Rick Santorum in the race for the Republican U.S. presidential nomination, the difficulty of a general election matchup against Democratic President Barack Obama became clearer.
Romney looked poised for victories in contests in Wisconsin, Maryland and Washington, D.C. on Tuesday, a sweep that would add pressure on conservative rival Santorum to yield to rising calls from party leaders for Republicans to rally behind Romney.
If Tuesday does not chase Santorum from the race, the Romney campaign is planning an aggressive push in Pennsylvania, the former senator's home state, to try to defeat him there on April 24 and land a decisive blow.
Romney leads in opinion polls among Republicans in five other states voting that day and is within striking distance of Santorum in Pennsylvania. Romney is set to go there later this week, and his "Restore Our Future" Super PAC group is already spending there on TV air time.
"It would certainly be very challenging for him to go forward if he can't win his own home state," said a senior Romney campaign official, speaking on condition of anonymity. "We see an opportunity there."
Romney has a large lead over Santorum in the race to amass the 1,144 delegates need to clinch the Republican presidential nomination at the party's convention in August. Party leaders believe he will ultimately win it, but that the longer the race drags on, the harder it will be to defeat Obama in the November 6 election.
Santorum gave no indication that he planned to get out of the race despite a new poll that showed him trailing in Wisconsin, the most important primary on Tuesday.
"If I thought that prolonging this race was a detrimental thing for our (Republican) chances to win in the fall, I may take a different course, but I honestly sincerely believe that the best thing we could do is ... get the best candidate," Santorum said in Little Chute, Wisconsin.
If he does win the nomination as expected, Romney would face the challenge of defeating an incumbent president whose campaign operation is well-funded, organized and eager to pounce on any misstep. Romney also would enter the general election campaign at a distinct disadvantage among women voters, a bloc that could be critical in swinging the election.
A USA Today/Gallup poll found that women have helped Obama take a large lead over Romney in a dozen battleground states.
The poll showed support for Obama among women under the age of 50 surged from mid-February, putting the president ahead of the former Massachusetts governor by 51 percent against 42 percent overall. Obama led Romney among this group of women by two to one, the poll said.
The results appear to be fallout from the Republicans' presidential primary campaign in which Santorum criticized contraception as morally wrong and Romney pledged to end federal funding for the Planned Parenthood women's health organization that provides abortion services.
Romney has made a point of saying there would be no attempt to ban contraception under a Romney administration. But to curry favor with social conservatives, he has been vocal in his opposition to abortion.
The USA Today/Gallup poll surveyed 993 registered voters and was taken March 20-25 in Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin.
The Romney campaign has begun to plan how to move into a general election fight against Obama, looking at an increase in staffing and building up a rapid-response system to counter the Democrats' well-oiled campaign machine.
Romney, a multimillionaire who sometimes struggles to connect with ordinary people, is taking steps to hear regularly from everyday Americans. Aides said he has been holding private meetings with families who talk to him about their struggles making ends meet and paying for high gasoline prices.
But Romney faced an awkward moment at a town hall-style campaign event in Green Bay on Monday.
When Bret Hatch, a supporter of rival Republican candidate Ron Paul, stood up and began reading from a Mormon document and asked whether Romney's Mormon faith could be a concern in the election, Romney initially said he did not want to discuss religion.
But when asked by someone else later how to handle the question of whether he was out of touch, Romney told how being in a leadership role in his church had given him a better understanding of people's problems.
"Most Americans, by the way, are carrying a burden of some kind," he said. "It may be their own health difficulties. It may be concern about a job. It may be inability to pay for the home or the college they were hoping to pay for a child."
He added: "And one of the reasons I'm running for president of the United States is I want to help people, I want to lighten those burdens."
Additional reporting by Sam Youngman; Editing by Will Dunham