Banks have a challenge when Congress returns from summer recess next week. His name is John Neely Kennedy.

The freshman Republican senator from Louisiana is one of a handful of lawmakers who could squash the finance industry's dream of tweaking a key Consumer Financial Protection Bureau regulation. So far, he's not saying whether he will or won't.

The new rule would make it easier for customers to sue financial institutions, and banks have spent millions to keep arbitration as the required venue for dispute resolution instead. Lawmakers have a limited window of time to change the provision, and because the GOP's Senate majority is slim, Kennedy, a lawyer and former Democrat who pitches himself as a folksy Washington outsider, could be the one to cast the deciding vote.