Wall Street firms are launching a campaign to challenge the Obama administration’s proposal for a new tax on large financial firms to recoup bailout money handed out during the financial crisis. The New York Times reports a main lobbying group for the big banks, the Securities Industry and Financial Markets Association, has hired a top Supreme Court litigator to study a possible legal battle against the bank tax. The lobbying group claims the proposed tax is unconstitutional because it would unfairly single out and penalize big banks.