Romney set to beat Santorum in Wisconsin primary: poll By Lily Kuo WASHINGTON (Reuters) - Republican presidential candidate Mitt Romney appeared set to defeat his chief rival Rick Santorum in the Wisconsin primary on Tuesday, according to a Public Policy Polling survey. A win there for Romney would be another nail in the coffin for Santorum, a former senator for Pennsylvania and staunch conservative. As the primary contests enter their fourth month, Santorum is facing pressure from some Republicans to bow out of the race to be the party's nominee to oppose President Barack Obama in November. Romney was ahead of Santorum by 7 points in Wisconsin, according to the survey by Democratic polling firm Public Policy Polling, which was released late Sunday. Santorum's hopes of securing the nomination have faded as Romney, a former Massachusetts governor, has outpaced him in fundraising, endorsements from establishment Republicans and the tally of state delegates needed to win the nomination. Romney was also ahead of Santorum by 25 points in Maryland, according to the poll which was roughly in line with other recent surveys. Maryland and Washington, D.C. also hold primaries on Tuesday. The poll, which surveyed 609 likely Republican voters in Wisconsin and 500 in Maryland, found Romney gaining support among conservative groups that have previously tended to favor Santorum. Romney beat out Santorum among supporters of the conservative grassroots Tea Party movement in both states. In Maryland, Romney led Santorum among evangelical Christians by 3 percentage points, a statistical tie. "Increasingly Mitt Romney is eating into Rick Santorum's base," said Dean Debnam, president of Public Policy Polling. That would seem to be a sign GOP voters are ready for this race to be over. Santorum has vowed to stay in the race and may win primary races in May in states where his appeal to evangelical voters resonates, such as North Carolina, West Virginia, Indiana, Kentucky and possibly Texas, with its large haul of 155 delegates. The survey was conducted on March 31 and April 1. The margin of error for the Wisconsin poll was plus or minus 4 percent and for the Maryland survey plus or minus 4.4 percent. Editing by Frances Kerry