Republican Rick Santorum lashed out at chief rival Mitt Romney on Saturday as \"uniquely unqualified\" to challenge President Barack Obama in November\'s election and urged Ohio voters to join him in rejecting the party\'s old-boy establishment. On a busy day of campaigning ahead of Ohio\'s vital Republican primary on Tuesday, Santorum portrayed himself as a blue-collar underdog who would remain true to his conservative principles in battling heavy-handed government power. He said Romney, the former Massachusetts governor, had forfeited his ability to fight Obama\'s federal healthcare overhaul by backing a similar plan in Massachusetts that included an individual mandate to purchase insurance. \"He is uniquely unqualified to go against Barack Obama on the biggest issue in this election,\" Santorum told a crowd of about 400 in a hotel ballroom in Blue Ash, a Cincinnati suburb in heavily Republican southwest Ohio. Santorum is battling to hold a narrow lead in polls over Romney in Ohio, the biggest prize of the 10 states holding \"Super Tuesday\" nominating contests. Romney, a wealthy former head of a private equity firm, has a big financial and organizational edge on his Republican rivals. \"This race is going to be close in Ohio, we are going to be outspent, but we\'ve been outspent in every race so far,\" Santorum said. In response to the criticism, Romney\'s campaign issued a statement noting he had never supported an individual mandate on the federal level and believed states should be free to develop their own healthcare reforms. At a Republican dinner in Lima, Ohio, on Saturday night, Santorum acknowledged Romney had only backed a state-level healthcare mandate but said he was not impressed by the distinction. \"I know that\'s a difference, but it\'s hardly a rallying cry for the nation,\" Santorum said. Romney gained momentum heading into Tuesday after a double-win over Santorum in Michigan and Arizona this week, but a Santorum victory in Ohio would turn the frequently shifting Republican race upside down again and ensure a long, drawn-out battle for the nomination. \'NOT READY\' Romney\'s campaign criticized Santorum\'s failure to file full delegate slates in several Ohio districts, which makes him ineligible to win up to a quarter of the state\'s 66 delegates to the nominating convention in August. Santorum also failed to qualify for the ballot in Virginia, another Super Tuesday state. The slip-ups were evidence Santorum\'s campaign \"is simply not prepared to take on a Democrat machine that will raise and spend $1 billion,\" Rich Beeson, Romney\'s political director, said in a memo to reporters. Santorum told the Ohio crowd he was fighting Romney\'s \"old-boy network, the insiders.\" He described himself as a \"first-generation Italian American from a steel town in western Pennsylvania. We haven\'t had too many of those in the White House, it\'s about time we get one.\" Santorum, a staunch social conservative, said Obama and his fellow Democrats had encouraged an overactive government that undercut communities, families and churches by imposing its own values and views. \"You go into the neighborhoods in Cincinnati where there are no dads and where the churches have bailed out, where the community organizations don\'t exist. What do you find? Government everywhere,\" Santorum said. \"Do you find freedom? Do the people who live in those communities feel safe going out at night?\" he asked. Santorum conducted three public campaign events in southern and western Ohio on Saturday. On Sunday he will visit Tennessee and Oklahoma, which also have primaries on Tuesday, before returning to Ohio for the run-up to Tuesday\'s voting. Santorum\'s campaign has been dominated in the last few weeks by his comments on politicized social issues like abortion and birth control, but he has focused in Ohio on familiarizing voters with his biography and laying out his plans to resurrect the struggling economy. He said in Blue Ash that his plan to eliminate the corporate tax on manufacturing firms would help turn ailing Rust Belt economies into the \"stainless steel belt.\"