From big banks' exotic trades to the credit cards in people's wallets, a few contentious issues could upend a delicate political equilibrium as US lawmakers try to blend House and Senate bills into a single rewrite of banking regulations. The final measure, which President Barack Obama wants on his desk by July 4, is intended to prevent another financial crisis like the 2008 meltdown, which triggered a deep recession. Democratic Rep. Barney Frank, chairman of a panel resolving differences in the two bills, and Sen. Christopher Dodd, a Democrat who shepherded the Senate's measure, must fend off industry efforts to dilute the final legislation while holding together a Senate coalition that included only four Republicans. Typically, legislation gets watered down in the Senate. This time, the Senate version emerged tougher than the House bill. Frank agreed to make the Senate bill the base. “Throughout this process you have seen a desire by members not wanting to be seen voting with the banks,” said Edward Mills, a financial policy analyst at FBR Capital markets. The financial industry is no stranger to the lawmakers working on the legislation.