Santorum gains edge with conservative voters ahead of Michigan primary Rick Santorum ... the last man standing? Photograph: Jonathan Ernst/REUTERS Rick Santorum looks to be the last man standing for many conservative voters in the Republican presidential race after polls showed him pulling ahead of Mitt Romney nationally and in the important Michigan primary. Although Romney remains the favourite to win his party's nomination, the surveys will be a further blow to his chances of being elected president, as they show his own party is more divided than ever over his conservative credentials. The results suggest that many Republicans will stay away from the polls if Romney is their party's candidate and that the vicious primary battles have resulted in a surge in support for Barack Obama among independent voters. A Pew Research Center poll taken this week puts support for Santorum among Republican voters at 30%, two percentage points ahead of Romney. A month ago, Romney held a 31% to 14% lead over Santorum. A Public Policy Polling (PPP) survey released on Monday showed that Santorum has taken a significant lead in the Michigan primary in a fortnight. Santorum is at 39%, 15 percentage points ahead of Romney. The numbers are a stinging blow to Romney because he was born in Michigan and his father was governor of the state. The big loser is Newt Gingrich who, after his crushing victory over Romney in South Carolina last month, was calling on Santorum to quit the race to make way for him as the conservative candidate. But the former speaker of the House of Representatives appears to have been undone by the relentless attack adverts in support of Romney which focused on Gingrich's ethical violations in Congress, his work as a lobbyist and his serial adultery. Gingrich was also not helped by some of his own proposals, including establishing a colony on the moon. PPP said the results show that Santorum's rise "is attributable to two major factors: his own personal popularity (a stellar 67/23 favourability) and (Republican) voters increasingly souring on Gingrich." "Santorum's becoming something closer and closer to a consensus conservative candidate as Gingrich bleeds support," it said. Santorum, who has already won more contests and twice as many delegates as Gingrich, is focused on winning Michigan and then Ohio, another rust belt state where his campaign team believes his working class background will play well with blue collar conservatives. The Santorum campaign team's hope is that victories in the two states would force Gingrich out of the race. On Monday, the National Review, a prominent conservative publication, on Monday called on Gingrich to quit now. It would be a grave mistake for the party to make someone with such poor judgment and persistent unpopularity its presidential nominee. It is not clear whether Gingrich remains in the race because he still believes he could become president next year or because he wants to avenge his wounded pride: an ambiguity that suggests the problem with him as a leader. When he led Santorum in the polls, he urged the Pennsylvanian to leave the race. On his own arguments the proper course for him now is to endorse Santorum and exit," the magazine said in a leader. The polls reflect the evident division in the Republican party through the early primaries and caucuses as conservatives and evangelical Christians in particular search around for an alternative to Romney who is frequently regarded with suspicion over his shifting positions on abortion, government oversight of healthcare and spending. That was most starkly shown in Gingrich's win in South Carolina and Santorum's upset victories in Missouri, Minnesota and Colorado - a state Romney won in 2008. According to the Pew poll, Santorum commands almost twice as much support as Romney among conservatives, Tea Party supporters and white evangelicals. He also now soundly beats Gingrich with all three groups. Romney leads among those who describe themselves as moderate or liberal Republicans but it is not enough to overcome the deficit on the right of the party. The Pew poll suggests the vicious Republican campaign, which has in part been shaped by millions of dollars poured in by Super Pacs to attack advertising, has taken its toll on Romney showing growing doubts about his commitment to conservatism. Three months ago more than half of Republican voters saw Romney as a strong conservative. That figure has dropped to 42% while those with doubts about his conservatism has risen to 50%. Sarah Palin on Monday damningly described Romney's conservatism as "evolving." Romney's problem if he wins the Republican nomination will be to ensure that those party supporters who have doubts about him turn out in the presidential election. Anecdotal evidence from the campaign trail suggests that many so deeply dislike Obama that they will vote for whoever is the Republican candidate. But the Pew poll says that about one-third of Republican supporters believe the split in the party will keep some Republicans from supporting Romney. The principal beneficiary appears to be the president. Nationally, support for Obama has risen to 52% while backing for Romney has slipped back to 44%. Among independent voters, who will do a lot to decide the election, support for Obama has surged. The president has come from behind just a month ago, when he trailed Romney 40% to 50%, to lead by nine percentage points.