WASHINGTON—President Barack Obama is plowing ahead with a commission to tackle the federal debt despite resistance from Republican leaders. Mr. Obama will name former Clinton White House Chief of Staff Erskine Bowles and former Republican Sen. Alan Simpson as co-chairmen of the commission Thursday when he signs an executive order creating the panel, an administration official said. The commission’s job will be to help bring down the federal budget deficit to 3% of gross domestic product by 2015, compared with nearly 10% today, and to propose ways to hold down the surging costs of government programs such as Medicare, Medicaid and Social Security. The president will also ask the panel to look at the U.S. tax code and has not ruled out tax increases for the middle class should the commission deem them necessary.