JPMorgan Chase & Co. has given financial reformers at least two billion reasons to insist on more aggressive oversight of the banking industry. In the wake of last week’s trading loss, presidential contender Mitt Romney and other Republicans will have to rethink their rhetoric around gutting the Dodd-Frank Act – and more specifically, its Volcker Rule provision. Voters may no longer believe that big banks can manage their own risks, which leaves making banks smaller the alternative to tighter regulation.