PHILADELPHIA - Mitt Romney struggled to find support for his education proposals while campaigning at an urban school Thursday, one day after declaring education the “civil rights issue of our era.’’

The visit, the first by the likely Republican presidential nominee to such a school, came as he begins to court a broader cross-section of the electorate he needs to defeat President Obama in November. In a speech Wednesday, Romney proposed expanding charter schools, which are privately run but funded by taxpayers, and creating a voucher system in which poor and disabled students could attend private schools, also using public money.