JPMorgan lost $2bn (£1.2bn), and its outspoken chairman Jamie Dimon has lost some political credibility. He's been at the forefront of the argument against the Obama administration's attempt to bring in tighter financial regulation.
In particular he's trying to fight off the "Volcker rule", named after Paul Volcker, the former chairman of the Federal Reserve. It stops banks from investing in hedge funds.
Mr Dimon was winning. Now his company's huge losses strengthen the hand of those arguing in favour of the new regulations and leaves Mr Dimon looking slightly foolish, although some say the Volcker rule wouldn't have had any impact in this case.
This plays into November's elections because one of Mitt Romney's central arguments is that President Obama has tangled the economy up in red tape.
Financial regulation is at the heart of that argument. Republicans have been ferocious in their opposition to the new rules on banks.